1.
Avalanche transceiver
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Avalanche transceivers or avalanche beacon are a class of active radio beacon transceivers operating at 457 kHz and specialized for the purpose of finding people or equipment buried under snow. When the owner sets out on a descent, the transceiver is activated. A457 kHz beacon is a device that requires batteries. A ski suit may contain a passive RECCO transponder sewn into the clothing. Early avalanche beacons transmitted at 2.275 kHz, in 1986, the international frequency standard of 457 kHz was adopted, and this remains the standard today. Many companies manufacture beacons that comply with this standard, an avalanche beacon is not considered a preventive measure against possible avalanche burial, but rather it is a way to reduce the amount of time buried. This unit, functioning at 2.275 kHz, converted the frequency to a simple tone audible to the human ear. By following the tone to where it was loudest, the operator could use it to locate the buried beacon by using a grid searching technique. In 1986, IKAR adopted the frequency of 457 kHz, in 1996 ASTM adopted the 457 kHz standard. The following are the accepted international standards for Avalanche Transceivers operating on the 457 kHz frequency. In 1997, the first digital beacon was introduced at the Winter Outdoor Retailer show by Backcountry Access under the brand name Tracker, the Tracker DTS soon became the most widely used beacon in North America, and is still sold and used by many backcountry enthusiasts. Today, consumers have a range of choices for digital beacons from companies like Ortovox, Arva, Pieps, Mammut. There are two types of beacons, digital and analog. They both adhere to the standard as described above, and only differ in the method used to indicate to the user where the buried beacon is located. Most beacons currently being sold are digital, because of their ease of use. The original avalanche beacon was a beacon which transmitted the pulsed signal as an audible tone to the user. The tone gets louder when the user is closer to the transmitting beacon and these beacons have also been augmented with LEDs that provide a visual indication of signal strength, and earpieces to increase the ability of the listener to hear the tone. Digital transceivers take the strength of the signal and the emitted dipole flux pattern and compute distance, in order to calculate the emitted dipole flux pattern, a digital transceiver must have at least two antennas, although most modern transceivers have three
2.
Transmitter
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In electronics and telecommunications a transmitter or radio transmitter is an electronic device which generates a radio frequency alternating current. When a connected antenna is excited by this current, the antenna emits radio waves. The term transmitter is usually limited to equipment that generates radio waves for communication purposes, or radiolocation, such as radar and navigational transmitters. Generators of radio waves for heating or industrial purposes, such as ovens or diathermy equipment, are not usually called transmitters even though they often have similar circuits. The term is used more specifically to refer to a broadcast transmitter. This usage typically includes both the proper, the antenna, and often the building it is housed in. A transmitter can be a piece of electronic equipment, or an electrical circuit within another electronic device. A transmitter and a receiver combined in one unit is called a transceiver, the term transmitter is often abbreviated XMTR or TX in technical documents. The purpose of most transmitters is radio communication of information over a distance, the transmitter combines the information signal to be carried with the radio frequency signal which generates the radio waves, which is called the carrier signal. The information can be added to the carrier in several different ways, in an amplitude modulation transmitter, the information is added to the radio signal by varying its amplitude. In a frequency modulation transmitter, it is added by varying the signals frequency slightly. Many other types of modulation are used, the radio signal from the transmitter is applied to the antenna, which radiates the energy as radio waves. The antenna may be enclosed inside the case or attached to the outside of the transmitter, as in portable devices such as phones, walkie-talkies. In more powerful transmitters, the antenna may be located on top of a building or on a tower, and connected to the transmitter by a feed line. The first primitive radio transmitters were built by German physicist Heinrich Hertz in 1887 during his investigations of radio waves. These generated radio waves by a high voltage spark between two conductors, beginning in 1895 Guglielmo Marconi developed the first practical radio communication systems using spark transmitters. These spark-gap transmitters were used during the first three decades of radio, called the wireless telegraphy or spark era, vacuum tube transmitters took over because they were inexpensive and produced continuous waves, which could be modulated to transmit audio using amplitude modulation. This made possible commercial AM radio broadcasting, which began in about 1920, experimental television transmission had been conducted by radio stations since the late 1920s, but practical television broadcasting didnt begin until the 1940s
3.
Radio receiver
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In radio communications, a radio receiver is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna, the antenna intercepts radio waves and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information. The information produced by the receiver may be in the form of sound, a radio receiver may be a separate piece of electronic equipment, or an electronic circuit within another device. The most familiar form of radio receiver is a broadcast receiver, often just called a radio, the sound is produced either by a loudspeaker in the radio or an earphone which plugs into a jack on the radio. The radio requires electric power, provided either by batteries inside the radio or a cord which plugs into an electric outlet. All radios have a control to adjust the loudness of the audio. The frequency of radio stations is usually listed prominently in their advertising, in order to select a particular station to receive, the radio is adjusted to the frequency of the desired transmitter. In some radios this is done by the user turning a tuning knob until the station is heard in the radios loudspeaker. In most countries radio broadcasting is permitted using two different methods of modulation, that is, methods of adding the signal to the radio wave, AM and FM. In amplitude modulation the strength of the signal is varied by the audio signal. AM broadcasting is permitted on AM broadcast bands between 148 and 283 kHz in the low range and 526 and 1706 kHz in the medium frequency range of the radio spectrum. In frequency modulation the frequency of the signal is varied slightly by the audio signal. FM broadcasting is permitted in the FM broadcast bands between about 65 and 108 MHz in the high frequency range. The exact frequency ranges vary somewhat in different countries, radios sold in each receive the correct frequency range for that country. Most broadcast radios, called AM/FM radios, can receive both AM and FM bands, and have a switch to select which band to receive. Limited AM broadcasting is permitted in parts of the high frequency band called the shortwave band. Shortwave listening requires a receiver that can receive these bands, called a shortwave receiver, at these frequencies, radio waves transmitted into the sky can reflect from a layer in the atmosphere called the ionosphere, returning to earth at transcontinental distances. So shortwaves are used for long distance international broadcasting, often by governmental public service broadcasting organizations like the BBC, due to their lower frequency, AM radio stations can often be received at longer distances than FM stations, at hundreds of miles
4.
Transponder
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In telecommunication, a transponder is one of two types of devices. The term is a portmanteau for transmitter-responder and it is variously abbreviated as XPDR, XPNDR, TPDR or TP. A communications satellite’s channels are called transponders, because each is a separate transceiver or repeater, with digital video data compression and multiplexing, several video and audio channels may travel through a single transponder on a single wideband carrier. Original analog video only has one channel per transponder, with subcarriers for audio, non-multiplexed radio stations can also travel in single channel per carrier mode, with multiple carriers per transponder. This allows each station to transmit directly to the satellite, rather than paying for a whole transponder, in optical fiber communications, a transponder is the element that sends and receives the optical signal from a fiber. A transponder is typically characterized by its rate and the maximum distance the signal can travel. The difference between the two is that transceivers interface electrically with the host system using an interface, whereas transponders use a parallel interface to do so. In this view, transponders provide easier-to-handle lower-rate parallel signals, but are bulkier, as such, transponders can be considered as two transceivers placed back-to-back. This view also seems to be held by e. g. Fujitsu, as a result, difference in transponder functionality also might influence the functional description of related optical modules like transceivers and muxponders. Primary radar works best with large aircraft, but not so well on small. Its range is limited by terrain and rain or snow and also detects unwanted objects such as automobiles, hills. Furthermore, it cannot always estimate the altitude of an aircraft, secondary radar overcomes these limitations but it depends on a transponder in the aircraft to respond to interrogations from the ground station to make the plane more visible. Another mode called Mode S is designed to help avoiding over-interrogation of the transponder, Mode S transponders are backward compatible with Modes A and C. Mode S is mandatory in controlled airspace in many countries. Some countries have required, or are moving towards requiring. In addition, navigational aids often have transponders called RACON designed to make them out on a ships radar screen. Many modern automobiles have keys with transponders hidden inside the head of the key. The user of the car may not even be aware that the transponder is there, when a key is inserted into the ignition lock cylinder and turned, the cars computer sends a radio signal to the transponder. Unless the transponder replies with a code, the computer will not allow the engine to be started
5.
Transverter
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In radio engineering, a transverter is a radio frequency device that consists of an upconverter and a downconverter in one unit. Transverters are used in conjunction with transceivers to change the range of frequencies over which the transceiver can communicate, in electrical power engineering, a transverter is a universal electrical power converter that can combine, convert, analyze and control any combinations of DC or AC power. Transverters are used in radio to convert radio transceivers designed for use on the HF or VHF bands to operate on even higher frequency bands. A transceiver used in fashion is referred to as an IF radio. Some transverter units include transmit/receive switching built into the design, whereas other units require external switching, the use of external switching is popular in applications where preamps and amplifiers are included. Transverters can also be used in applications where the frequency is lower than the transceiver frequency. Several low frequency bands are available around the world to amateur operators, licensed experimental stations. Transverters for these LF bands generally use HF transceivers as the IF radio, some are used for communications where one or more of the stations are underground. Transverters are used to convert and combine different types of power such as solar panels, batteries, wind generators, fuel cells. By automatically analyzing and converting the power between different voltages and AC or DC, it allows for energy to flow between all types of devices. With the advent of the Smart Grid it is becoming very popular since it combines renewable energy, demand management, transverters also correct for power factor locally, which creates significant reductions in transmission loss for the grid
6.
Repeater
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In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover distances or be received on the other side of an obstruction. Some types of repeaters broadcast a signal, but alter its method of transmission, for example. A broadcast relay station is a used in broadcast radio. When an information-bearing signal passes through a channel, it is progressively degraded due to loss of power. The longer the wire is, the power is lost. So with a long enough wire the call will not be audible at the other end, similarly, the farther from a radio station a receiver is, the weaker the radio signal, and the poorer the reception. A repeater is a device in a communication channel that increases the power of a signal and retransmits it. Since it amplifies the signal, it requires a source of electric power, the term repeater originated with telegraphy in the 19th century, and referred to an electromechanical device used to regenerate telegraph signals. Use of the term has continued in telephony and data communications and this is used to increase the range of telephone signals in a telephone line. They are most frequently used in trunklines that carry long distance calls, since the telephone is a duplex communication system, the wire pair carries two audio signals, one going in each direction. So telephone repeaters have to be bilateral, amplifying the signal in both directions without causing feedback, which complicates their design considerably, telephone repeaters were the first type of repeater and were some of the first applications of amplification. The development of telephone repeaters between 1900 and 1915 made long distance phone service possible, however most telecommunications cables are now fiber optic cables which use optical repeaters. Submarine cable repeater This is a type of telephone used in underwater submarine telecommunications cables. This is used to increase the range of signals in a fiber optic cable, digital information travels through a fiber optic cable in the form of short pulses of light. The light is made up of particles called photons, which can be absorbed or scattered in the fiber, however, optical amplifiers are being developed for repeaters to amplify the light itself without the need of converting it to an electric signal first. Some repeaters have been powered by light energy transmitted down the fiber with the signal and this is used to extend the range of coverage of a radio signal. A radio repeater usually consists of a receiver connected to a radio transmitter
7.
Two-way radio
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A two-way radio is a radio that can do both transmit and receive a signal, unlike a broadcast receiver which only receives content. A two-way radio allows the operator to have a conversation with other similar radios operating on the radio frequency. Two-way radios are available in mobile, stationary base and hand-held portable configurations, hand-held radios are often called walkie-talkies, handie-talkies, or just hand-helds. Two-way radio systems operate in a half-duplex mode, that is, the operator can talk, or he can listen. A push-to-talk or Press To Transmit button activates the transmitter, when it is released the receiver is active, a mobile phone or cellular telephone is an example of a two-way radio that can transmit and receive at the same time, i. e. in full-duplex mode. Full-duplex is generally achieved by the use of two different frequencies or by frequency-sharing methods to carry the two directions of the conversation simultaneously, methods for mitigating the self interference caused by simultaneous same-frequency transmission and reception include using two antennas, or dynamic solid-state filters. Installation of receivers and transmitters at the fixed location allowed exchange of messages wirelessly. As early as 1907, two-way telegraphy traffic across the Atlantic Ocean was commercially available, by 1912 commercial and military ships carried both transmitters and receivers, allowing two-way communication in close to real-time with a ship that was out of sight of land. The first truly mobile two-way radio was developed in Australia in 1923 by Senior Constable Frederick William Downie of the Victorian Police. The Victoria Police were the first in the world to use communication in cars. The first sets took up the back seat of the Lancia patrol cars. As radio equipment became more powerful, compact, and easier to use, during World War II walkie-talkie hand-held radio transceivers were extensively used by air and ground troops, both by the Allies and the Axis. Early two-way schemes allowed only one station to transmit at a time while others listened, the first radio systems could not transmit voice. This required training of operators in use of Morse code, on a ship, the radio operating officers typically had no other duties than handling radio messages. When voice transmission possible, dedicated operators were no longer required. Two-way radio systems can be classified in several ways depending on their attributes, conventional radios operate on fixed RF channels. In the case of radios with multiple channels, they operate on one channel at a time, the proper channel is selected by a user. The user operates a channel selector on the control panel to pick the appropriate channel
8.
High frequency
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High frequency is the ITU designation for the range of radio frequency electromagnetic waves between 3 and 30 MHz. It is also known as the band or decameter wave as its wavelengths range from one to ten decameters. Frequencies immediately below HF are denoted medium frequency, while the band of higher frequencies is known as the very high frequency band. The HF band is a part of the shortwave band of frequencies. The band is used by shortwave broadcasting stations, aviation communication, government time stations, weather stations, amateur radio and citizens band services. By this method HF radio waves can travel beyond the horizon, around the curve of the Earth and it depends on the angle of incidence of the waves, it is lowest when the waves are directed straight upwards, and is higher with less acute angles. This means that at longer distances, where the waves graze the ionosphere at a blunt angle. The lowest usable frequency depends on the absorption in the layer of the ionosphere. This absorption is stronger at low frequencies and is stronger with increased solar activity. When all factors are at their optimum, worldwide communication is possible on HF, at many other times it is possible to make contact across and between continents or oceans. At worst, when a band is dead, no communication beyond the limited groundwave paths is possible no matter what powers, on such an open band, interference originating over a wide area affects many potential users. These issues are significant to military, safety and amateur radio users of the HF bands, other standards development such as STANAG5066 provides for error free data communications through the use of ARQ protocols. Noise, especially man-made interference from devices, tends to have a great effect on the HF bands. In recent years, concerns have risen among certain users of the HF spectrum over broadband over power lines Internet access and this is due to the frequencies on which BPL operates and the tendency for the BPL signal to leak from power lines. Some BPL providers have installed notch filters to block out certain portions of the spectrum, other electronic devices including plasma televisions can also have a detrimental effect on the HF spectrum. In aviation, HF communication systems are required for all trans-oceanic flights and these systems incorporate frequencies down to 2 MHz to include the 2182 kHz international distress and calling channel. The upper section of HF shares many characteristics with the part of VHF. The parts of this section not allocated to radio are used for local communications
9.
Spectrum analyzer
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A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument. The primary use is to measure the power of the spectrum of known and unknown signals, optical spectrum analyzers also exist, which use direct optical techniques such as a monochromator to make measurements. These parameters are useful in the characterization of electronic devices, such as wireless transmitters, the display of a spectrum analyzer has frequency on the horizontal axis and the amplitude displayed on the vertical axis. To the casual observer, a spectrum analyzer looks like an oscilloscope and, in fact, the first spectrum analyzers, in the 1960s, were swept-tuned instruments. Following the discovery of the fast Fourier transform in 1965, the first FFT-based analyzers were introduced in 1967, today, there are three basic types of analyzer, the swept-tuned spectrum analyzer, the vector signal analyzer, and the real-time spectrum analyzer. Spectrum analyzer types are distinguished by the used to obtain the spectrum of a signal. By sweeping the receivers center-frequency through a range of frequencies, the output is also a function of frequency, but while the sweep centers on any particular frequency, it may be missing short-duration events at other frequencies. An FFT analyzer computes a time-sequence of periodograms, FFT refers to a particular mathematical algorithm used in the process. This is commonly used in conjunction with a receiver and analog-to-digital converter, as above, the receiver reduces the center-frequency of a portion of the input signal spectrum, but the portion is not swept. The purpose of the receiver is to reduce the rate that the analyzer must contend with. With a sufficiently low sample-rate, FFT analyzers can process all the samples, Spectrum analyzers tend to fall into four form factors, benchtop, portable, handheld and networked. This form factor is useful for applications where the spectrum analyzer can be plugged into AC power, bench top spectrum analyzers have historically offered better performance and specifications than the portable or handheld form factor. Bench top spectrum analyzers normally have multiple fans to dissipate heat produced by the processor, due to their architecture, bench top spectrum analyzers typically weigh more than 30 pounds. Some bench top spectrum analyzers offer optional battery packs, allowing them to be used away from AC power and this type of analyzer is often referred to as a portable spectrum analyzer. This form factor is useful for any applications where the spectrum analyzer needs to be taken outside to make measurements or simply carried while in use, attributes that contribute to a useful portable spectrum analyzer include, Optional battery-powered operation to allow the user to move freely outside. Clearly viewable display to allow the screen to be read in bright sunlight and this form factor is useful for any application where the spectrum analyzer needs to be very light and small. Handheld analyzers usually offer a limited capability relative to larger systems, attributes that contribute to a useful handheld spectrum analyzer include, Very low power consumption. Battery-powered operation while in the field to allow the user to move freely outside and this form factor does not include a display and these devices are designed to enable a new class of geographically-distributed spectrum monitoring and analysis applications
10.
Digital signal processing
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Digital signal processing is the use of digital processing, such as by computers, to perform a wide variety of signal processing operations. The signals processed in this manner are a sequence of numbers that represent samples of a variable in a domain such as time, space. Digital signal processing and analog signal processing are subfields of signal processing, digital signal processing can involve linear or nonlinear operations. Nonlinear signal processing is closely related to system identification and can be implemented in the time, frequency. DSP is applicable to both streaming data and static data, the increasing use of computers has resulted in the increased use of, and need for, digital signal processing. To digitally analyze and manipulate an analog signal, it must be digitized with an analog-to-digital converter, sampling is usually carried out in two stages, discretization and quantization. Discretization means that the signal is divided into equal intervals of time, quantization means each amplitude measurement is approximated by a value from a finite set. Rounding real numbers to integers is an example, the Nyquist–Shannon sampling theorem states that a signal can be exactly reconstructed from its samples if the sampling frequency is greater than twice the highest frequency of the signal. In practice, the frequency is often significantly higher than twice that required by the signals limited bandwidth. Theoretical DSP analyses and derivations are typically performed on discrete-time signal models with no amplitude inaccuracies, numerical methods require a quantized signal, such as those produced by an analog-to-digital converter. The processed result might be a frequency spectrum or a set of statistics, but often it is another quantized signal that is converted back to analog form by a digital-to-analog converter. In DSP, engineers usually study digital signals in one of the domains, time domain, spatial domain, frequency domain. They choose the domain in which to process a signal by making an assumption as to which domain best represents the essential characteristics of the signal. The most common processing approach in the time or space domain is enhancement of the signal through a method called filtering. Digital filtering generally consists of linear transformation of a number of surrounding samples around the current sample of the input or output signal. There are various ways to characterize filters, for example, A linear filter is a transformation of input samples. A causal filter uses only samples of the input or output signals. A non-causal filter can usually be changed into a filter by adding a delay to it
11.
Radio
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When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form, Radio systems need a transmitter to modulate some property of the energy produced to impress a signal on it, for example using amplitude modulation or angle modulation. Radio systems also need an antenna to convert electric currents into radio waves, an antenna can be used for both transmitting and receiving. The electrical resonance of tuned circuits in radios allow individual stations to be selected, the electromagnetic wave is intercepted by a tuned receiving antenna. Radio frequencies occupy the range from a 3 kHz to 300 GHz, a radio communication system sends signals by radio. The term radio is derived from the Latin word radius, meaning spoke of a wheel, beam of light, however, this invention would not be widely adopted. The switch to radio in place of wireless took place slowly and unevenly in the English-speaking world, the United States Navy would also play a role. Although its translation of the 1906 Berlin Convention used the terms wireless telegraph and wireless telegram, the term started to become preferred by the general public in the 1920s with the introduction of broadcasting. Radio systems used for communication have the following elements, with more than 100 years of development, each process is implemented by a wide range of methods, specialised for different communications purposes. Each system contains a transmitter, This consists of a source of electrical energy, the transmitter contains a system to modulate some property of the energy produced to impress a signal on it. This modulation might be as simple as turning the energy on and off, or altering more subtle such as amplitude, frequency, phase. Amplitude modulation of a carrier wave works by varying the strength of the signal in proportion to the information being sent. For example, changes in the strength can be used to reflect the sounds to be reproduced by a speaker. It was the used for the first audio radio transmissions. Frequency modulation varies the frequency of the carrier, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal. FM has the capture effect whereby a receiver only receives the strongest signal, Digital data can be sent by shifting the carriers frequency among a set of discrete values, a technique known as frequency-shift keying. FM is commonly used at Very high frequency radio frequencies for high-fidelity broadcasts of music, analog TV sound is also broadcast using FM. Angle modulation alters the phase of the carrier wave to transmit a signal
12.
Amateur radio
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The amateur radio service is established by the International Telecommunication Union through the International Telecommunication Regulations. National governments regulate technical and operational characteristics of transmissions and issue individual stations licenses with a call sign. Prospective amateur operators are tested for their understanding of key concepts in electronics, according to an estimate made in 2011 by the American Radio Relay League, two million people throughout the world are regularly involved with amateur radio. About 830,000 amateur radio stations are located in IARU Region 2 followed by IARU Region 3 with about 750,000 stations, a significantly smaller number, about 400,000, are located in IARU Region 1. The origins of amateur radio can be traced to the late 19th century, the First Annual Official Wireless Blue Book of the Wireless Association of America, produced in 1909, contains a list of amateur radio stations. This radio callbook lists wireless telegraph stations in Canada and the United States, as with radio in general, amateur radio was associated with various amateur experimenters and hobbyists. Amateur radio enthusiasts have significantly contributed to science, engineering, industry, research by amateur operators has founded new industries, built economies, empowered nations, and saved lives in times of emergency. Ham radio can also be used in the classroom to teach English, map skills, geography, math, science, the term ham radio was first a pejorative that mocked amateur radio operators with a 19th-century term for being bad at something, like ham-fisted or ham actor. It had already used for bad wired telegraph operators. Subsequently, the community adopted it as a moniker, much like the Know-Nothing Party, or other groups. Other, more entertaining explanations have grown up throughout the years, the many facets of amateur radio attract practitioners with a wide range of interests. Many amateurs begin with a fascination of radio communication and then combine other personal interests to make pursuit of the hobby rewarding, some of the focal areas amateurs pursue include radio contesting, radio propagation study, public service communication, technical experimentation, and computer networking. Amateur radio operators use various modes of transmission to communicate, the two most common modes for voice transmissions are frequency modulation and single sideband. FM offers high quality audio signals, while SSB is better at long distance communication when bandwidth is restricted. Radiotelegraphy using Morse code, also known as CW from continuous wave, is the extension of landline telegraphy developed by Samuel Morse. Morse, using internationally agreed message encodings such as the Q code, a similar legacy mode popular with home constructors is amplitude modulation, pursued by many vintage amateur radio enthusiasts and aficionados of vacuum tube technology. Demonstrating a proficiency in Morse code was for years a requirement to obtain an amateur license to transmit on frequencies below 30 MHz. Following changes in regulations in 2003, countries are no longer required to demand proficiency
13.
Walkie-talkie
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A walkie-talkie is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been credited to Donald L. Hings, radio engineer Alfred J. Gross. First used for infantry, similar designs were created for field artillery and tank units, typical walkie-talkies resemble a telephone handset, with a speaker built into one end and a microphone in the other and an antenna mounted on the top of the unit. They are held up to the face to talk, a walkie-talkie is a half-duplex communication device, multiple walkie-talkies use a single radio channel, and only one radio on the channel can transmit at a time, although any number can listen. The transceiver is normally in receive mode, when the user wants to talk he presses a button that turns off the receiver. The walkie-talkie was developed by the US military during World War 2, the first radio transceiver to be widely nicknamed Walkie-Talkie was the backpacked Motorola SCR-300, created by an engineering team in 1940 at the Galvin Manufacturing Company. The team consisted of Dan Noble, who conceived of the design using frequency modulation, Henryk Magnuski, who was the principal RF engineer, Marion Bond, Lloyd Morris, the first hand-held walkie-talkie was the AM SCR-536 transceiver also made by Motorola, named the Handie-Talkie. The terms are often confused today, but the original walkie-talkie referred to the back mounted model, both devices used vacuum tubes and were powered by high voltage dry cell batteries. Canadian inventor Donald Hings is also credited with the invention of the walkie-talkie and he called the system a packset, but it later became known as the walkie-talkie. In 2001, Hings was formally decorated for its significance to the war effort, Hings model C-58 Handy-Talkie was in military service by 1942, the result of a secret R&D effort that began in 1940. Following World War II, Raytheon developed the SCR-536s military replacement, the AN/PRC-6 circuit used 13 vacuum tubes, a second set of 13 tubes was supplied with the unit as running spares. The unit was set with one crystal which could be changed to a different frequency in the field by replacing the crystal. It used a 24 inch whip antenna, there was an optional handset H-33C/PT that could be connected to the AN/PRC-6 by a 5-foot cable. An adjustable strap was provided for carrying and support while operating, the AN/PRC-68 was first produced in 1976 by Magnavox, was issued to the Marines in the 1980s, and was adopted by the US Army as well. Public safety or commercial users generally refer to their handhelds simply as radios, surplus Motorola Handie Talkies found their way into the hands of ham radio operators immediately following World War II. Motorolas public safety radios of the 1950s and 1960s, were loaned or donated to ham groups as part of the Civil Defense program, to avoid trademark infringement, other manufacturers use designations such as Handheld Transceiver or Handie Transceiver for their products. Some cellular telephone networks offer a push-to-talk handset that allows operation over the cellular network. However, the provider must be accessible
14.
Citizens band radio
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Citizens band radio is, in many countries, a system of short-distance radio communications between individuals typically on a selection of 40 channels within the 27 MHz band. Citizens band is distinct from other personal radio service allocations such as FRS, GMRS, MURS, UHF CB, in many countries, CB operation does not require a license, and it may be used for business or personal communications. Like many other radio services, citizens band channels are shared by many users. Only one station may transmit at a time, other stations must listen and it is customary for stations waiting to use a shared channel to broadcast the single word Break during a lull in the conversation. This informs people using the channel that others are waiting, a number of countries have created similar radio services, with varying technical standards and requirements for licensing. While they may be known by names, such as the General Radio Service in Canada, they often use similar frequencies, have similar uses. Although licenses may be required, eligibility is generally simple, some countries also have personal radio services in the UHF band, such as the European PMR446 and the Australian UHF CB. The citizens band radio service originated in the United States as one of personal radio services regulated by the Federal Communications Commission. These services began in 1945 to permit citizens a radio band for personal communication, in 1948, the original CB radios were designed for operation on the 460–470 MHz UHF band. There were two classes of CB radio, A and B, Class B radios had simpler technical requirements, and were limited to a smaller frequency range. Al Gross established the Citizens Radio Corporation during the late 1940s to manufacture Class B handhelds for the general public, ultra-high frequency radios, at the time, were neither practical nor affordable for the average consumer. On September 11,1958 the Class D CB service was created on 27 MHz, there were only 23 channels at the time, the first 22 were taken from the former amateur radio service 11-meter band, and channel 23 was shared with radio-controlled devices. Some hobbyists continue to use the designation 11 meters to refer to the Citizens Band, part 95 of the Code of Federal Regulations regulates the Class D CB service, on the 27 MHz band, since the 1970s and continuing today. Most of the 460–470 MHz band was reassigned for business and public-safety use, Class B CB is a more distant ancestor of the Family Radio Service. The Multi-Use Radio Service is another two-way radio service in the VHF high band, an unsuccessful petition was filed in 1973 to create a Class E CB service at 220 MHz, which was opposed by amateur radio organizations. There are several classes of personal radio services for specialized purposes. During the 1960s, the service was popular among small businesses, truck drivers, CB clubs were formed, a CB slang language evolved alongside 10-codes, similar to those used in emergency services. After the 1973 oil crisis the U. S. government imposed a nationwide 55 mph speed limit, One leader was able to almost single-handedly coordinate an interstate highway blockade of hundreds of tractor-trailers in eastern Pennsylvania using the citizens band radio in his truck
15.
Telephone
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A telephone, or phone, is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. In 1876, Scottish emigrant Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice and this instrument was further developed by many others. The telephone was the first device in history that people to talk directly with each other across large distances. Telephones rapidly became indispensable to businesses, government, and households, the essential elements of a telephone are a microphone to speak into and an earphone which reproduces the voice in a distant location. Until approximately the 1970s most telephones used a dial, which was superseded by the modern DTMF push-button dial. The receiver and transmitter are usually built into a handset which is held up to the ear, the dial may be located either on the handset, or on a base unit to which the handset is connected. The transmitter converts the sound waves to electrical signals which are sent through the network to the receiving phone. The receiving telephone converts the signals into audible sound in the receiver, telephones permit duplex communication, meaning they allow the people on both ends to talk simultaneously. The first telephones were connected to each other from one customers office or residence to another customers location. Being impractical beyond just a few customers, these systems were replaced by manually operated centrally located switchboards. For greater mobility, various systems were developed for transmission between mobile stations on ships and automobiles in the middle 20th century. Hand-held mobile phone]s was introduced for personal service starting in 1973, by the late 1970s several mobile telephone networks operated around the world. In 1983, the Advanced Mobile Phone System was launched, offering a standardized technology providing portability for users far beyond the residence or office. These analog cellular system evolved into digital networks with better security, greater capacity, better regional coverage, the public switched telephone network, with its hierarchical system of many switching centers, interconnects telephones around the world for communication with each other. With the standardized international numbering system, E.164, each line has an identifying telephone number. Although originally designed for voice communications, convergence has enabled most modern cell phones to have many additional capabilities. Since 1999, the trend for mobile phones is smartphones that integrate all mobile communication, a traditional landline telephone system, also known as plain old telephone service, commonly carries both control and audio signals on the same twisted pair of insulated wires, the telephone line. The control and signaling equipment consists of three components, the ringer, the hookswitch, and a dial, the ringer, or beeper, light or other device, alerts the user to incoming calls
16.
Sound recording and reproduction
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Sound recording and reproduction is an electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording, prior to the development of analog recording, there were mechanical systems for reproducing instrumental music, such as wind-up music boxes and later, in the late 19th century, player pianos. Analog sound reproduction is the process, with a bigger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves. Digital recording and reproduction converts the sound signal picked up by the microphone to a digital form by the process of digitization. This lets the audio data be stored and transmitted by a variety of media. Whereas successive copies of an analog recording tend to degrade in quality, as noise is added. A digital audio signal must be reconverted to analog form during playback before it is amplified and connected to a loudspeaker to produce sound, long before sound was first recorded on cylinders or records, music was recorded—first by written music notation, then also by mechanical devices. Fowler, this. cylinder with raised pins on the surface remained the device to produce and reproduce music mechanically until the second half of the nineteenth century. The Banu Musa brothers also invented an automatic flute player, which appears to have been the first programmable machine, according to Fowler, the automata were a robot band that performed. more than fifty facial and body actions during each musical selection. In the 14th century, Flanders introduced a mechanical bell-ringer controlled by a rotating cylinder, similar designs appeared in barrel organs, musical clocks, barrel pianos, and musical boxes. A music box is a musical instrument that produces sounds by the use of a set of pins placed on a revolving cylinder or disc so as to pluck the tuned teeth of a steel comb. They were developed from musical snuff boxes of the 18th century, some of the more complex boxes also have a tiny drum and/or bells, in addition to the metal comb. The fairground organ, developed in 1892, used a system of accordion-folded punched cardboard books, the player piano, first demonstrated in 1876, used a punched paper scroll that could store an long piece of music. The most sophisticated of the rolls were hand-played, meaning that the roll represented the actual performance of an individual. This technology to record a live performance onto a piano roll was not developed until 1904, piano rolls were in continuous mass production from 1896 to 2008. A1908 U. S. Supreme Court copyright case noted that, in 1902 alone, the use of piano rolls began to decline in the 1920s although one type is still being made today. The first device that could record actual sounds as they passed through the air was the phonautograph, the earliest known recordings of the human voice are phonautograph recordings, called phonautograms, made in 1857. They consist of sheets of paper with sound-wave-modulated white lines created by a stylus that cut through a coating of soot as the paper was passed under it
17.
Mobile phone
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A mobile phone is a portable telephone that can make and receive calls over a radio frequency link while the user is moving within a telephone service area. The radio frequency link establishes a connection to the systems of a mobile phone operator. Most modern mobile telephone services use a network architecture, and, therefore. Mobile phones which offer these and more general computing capabilities are referred to as smartphones, the first handheld mobile phone was demonstrated by John F. Mitchell and Martin Cooper of Motorola in 1973, using a handset weighing c.4.4 lbs. In 1983, the DynaTAC 8000x was the first commercially available mobile phone. From 1983 to 2014, worldwide mobile phone subscriptions grew to seven billion, penetrating 100% of the global population. In first quarter of 2016, the top smartphone manufacturers were Samsung, Apple, a handheld mobile radio telephone service was envisioned in the early stages of radio engineering. In 1917, Finnish inventor Eric Tigerstedt filed a patent for a pocket-size folding telephone with a thin carbon microphone. Early predecessors of cellular phones included analog radio communications from ships, the race to create truly portable telephone devices began after World War II, with developments taking place in many countries. These 0G systems were not cellular, supported few simultaneous calls, the first handheld mobile phone was demonstrated by John F. Mitchell and Martin Cooper of Motorola in 1973, using a handset weighing c.4.4 lbs. The first commercial automated cellular network was launched in Japan by Nippon Telegraph and this was followed in 1981 by the simultaneous launch of the Nordic Mobile Telephone system in Denmark, Finland, Norway, and Sweden. Several other countries followed in the early to mid-1980s. These first-generation systems could support far more simultaneous calls but still used analog cellular technology, in 1983, the DynaTAC 8000x was the first commercially available handheld mobile phone. In 1991, the digital cellular technology was launched in Finland by Radiolinja on the GSM standard. This sparked competition in the sector as the new operators challenged the incumbent 1G network operators, ten years later, in 2001, the third generation was launched in Japan by NTT DoCoMo on the WCDMA standard. This was followed by 3. 5G, 3G+ or turbo 3G enhancements based on the high-speed packet access family, allowing UMTS networks to have data transfer speeds. By 2009, it had become clear that, at point, 3G networks would be overwhelmed by the growth of bandwidth-intensive applications. Consequently, the industry began looking to data-optimized fourth-generation technologies, with the promise of speed improvements up to ten-fold over existing 3G technologies
18.
Radiotelephone
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A radiotelephone is a communications system for transmission of speech over radio. Radiotelephone systems are not necessarily interconnected with the land line telephone network. Radiotelephony means transmission of sound by radio, in contrast to radiotelegraphy or video transmission, the word phone has a long precedent beginning with early US wireless voice systems. The term means voice as opposed to telegraph or Morse code and this would include systems fitting into the category of two-way radio or one-way voice broadcasts such as coastal maritime weather. The term is popular in the amateur radio community and in US Federal Communications Commission regulations. A standard landline telephone allows both users to talk and listen simultaneously, effectively there are two channels between the two end-to-end users of the system. It is, however, the most comfortable method of communication for users. The most common method of working for radiotelephones is half-duplex, operation, which one person to talk. If a single channel is used, both take turns to transmit on it. An eavesdropper would hear both sides of the conversation, dual-frequency working splits the communication into two separate channels, but only one is used to transmit at a time. The end users have the experience as single frequency simplex. The user presses a switch on the transmitter when they wish to talk—this is called the press-to-talk switch or PTT. It is usually fitted on the side of the microphone or other obvious position, users may use a special code-word such as over to signal that they have finished transmitting, or it may follow from the conversation. Radiotelephones may operate at any frequency where they are licensed to do so and they may use simple modulation schemes such as AM or FM, or more complex techniques such as digital coding, spread spectrum, and so on. Licensing terms for a band will usually specify the type of modulation to be used. For example, airband radiotelephones used for air to ground communication between pilots and controllers operates in the VHF band from 118.0 to 136.975 MHz, Radiotelephone receivers are usually designed to a very high standard, and are usually of the double-conversion superhet design. Multiple channels are provided using a frequency synthesizer. Receivers usually features a squelch circuit to cut off the output from the receiver when there is no transmission to listen to
19.
Cordless telephone
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A cordless telephone or portable telephone is a telephone in which the handset is portable and communicates with the body of the phone by radio, instead of being attached by a cord. The base station is connected to the network through a telephone line as a corded telephone is. The range is limited, usually to the building or some short distance from the base station. The base station on subscriber premises is what differentiates a cordless telephone from a mobile telephone, in specialized models, base stations are maintained by a commercial mobile network operator and users subscribe to the service. In 1994, digital cordless phones in the 900 MHz frequency range were introduced, Digital signals allowed the phones to be more secure and decreased eavesdropping—it was relatively easy to eavesdrop on analog cordless phone conversations. In 1995, digital spread spectrum was introduced for cordless phones, unlike a corded telephone, a cordless telephone needs mains electricity to power the base station. The cordless handset is powered by a battery, which is charged when the handset is stored in its cradle. In 1968, she sold her rights to the phone to a manufacturer who modified it for practical use. Bell Labs Lineless Telephone 1963-1967 Beginning in 1963, a team of Bell Laboratories engineers were given the task of developing a practical. Clemency, M. Rosenthal, and W. Zinsmeister, under the direction of W. D. Goodale, by 1964, breadboard models were working in the lab. During 1964-65 these were refined and packaged to test around the Bell Labs Holmdel N. J. building, the system operated under an experimental license on crystal controlled channels in the 35 and 43 MHz bands using FM modulation, a low power transmitter and a sensitive superhet receiver. Full supervision of all functions, including on-off hook and dialing was provided via an out of band tone supervision system. The user end of the system was packaged to look like a telephone handset. The other end – the base station was a small box connected to the telephone network. About 50 units were built in a Western Electric model shop in Andover Mass. for field trails in two Bell System locations in the Boston and Phoenix area, the overall project was described in the Bell Laboratories Record, Volume 45, pages 202-203. He was awarded US3449750 in June 1969 He, sweigert was an active proponent for directly coupling consumer electronics to the AT&T-owned telephone lines in the late 1960s. The original cordless phones, like the Carterfone, were connected to the Public Switched Telephone Network. A single logic tone is transmitted and detected for all logical control for ring signals, on-hook and off-hook signals, in the United States, seven frequency bands have been allocated by the Federal Communications Commission for uses that include cordless phones
20.
Base station
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Base station is – according to article 1.71 of the International Telecommunication Union´s ITU Radio Regulations – defined as A land station in the land mobile service. In mobile telephony it provides the connection between mobile phones and the telephone network. In a computer network it is a transceiver acting as a router for computers in the network, in the context of external land surveying, a base station is a GPS receiver at an accurately-known fixed location which is used to derive correction information for nearby portable GPS receivers. It typically consists of a transmitter and wireless router. The base station is one end of a communications link, the other end is a movable vehicle-mounted radio or walkie-talkie. Examples of base station uses in two-way radio include the dispatch of tow trucks, professional base station radios are often one channel. In lightly used stations, a multi-channel unit may be employed. In heavily used systems, the capability for additional channels, where needed, is accomplished by installing an additional station for each channel. Each base station appears as a channel on the dispatch center control console. In a properly designed dispatch center with several members, this allows each dispatcher to communicate simultaneously, independently of one another. For example, a taxi company dispatch center may have one station on a high-rise building in Boston. Each taxi dispatcher could communicate with taxis in either Boston or Providence by selecting the respective base station on his or her console, in dispatching centers it is common for eight or more radio base stations to be connected to a single dispatching console. Dispatching personnel can tell which channel a message is being received on by a combination of local protocol, unit identifiers, volume settings, a typical console has two speakers identified as select and unselect. Audio from a selected channel is routed to the select speaker. Each channel has a light which flashes when someone talks on the associated channel. Base stations can be controlled or remote controlled. Local controlled base stations are operated by front panel controls on the base station cabinet, remote control base stations can be operated over tone- or DC-remote circuits. The dispatch point console and remote base station are connected by leased private line telephone circuits, the consoles multiplex transmit commands onto remote control circuits
21.
Modem
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A modem is a network hardware device that modulates one or more carrier wave signals to encode digital information for transmission and demodulates signals to decode the transmitted information. The goal is attempting to produce a signal that can be transmitted easily, modems can be used with any means of transmitting analog signals, from light emitting diodes to radio. Modems are generally classified by the amount of data they can send in a given unit of time, usually expressed in bits per second. Modems can also be classified by their rate, measured in baud. The baud unit denotes symbols per second, or the number of times per second the modem sends a new signal. For example, the ITU V.21 standard used audio frequency shift keying with two frequencies, corresponding to two distinct symbols, to carry 300 bits per second using 300 baud. By contrast, the original ITU V.22 standard, which could transmit and receive four distinct symbols, news wire services in the 1920s used multiplex devices that satisfied the definition of a modem. However, the function was incidental to the multiplexing function, so they are not commonly included in the history of modems. S. SAGE modems were described by AT&Ts Bell Labs as conforming to their newly published Bell 101 dataset standard, while they ran on dedicated telephone lines, the devices at each end were no different from commercial acoustically coupled Bell 101,110 baud modems. The 201A and 201B Data-Phones were synchronous modems using two-bit-per-baud phase-shift keying, the famous Bell 103A dataset standard was also introduced by AT&T in 1962. It provided full-duplex service at 300 bit/s over normal phone lines, frequency-shift keying was used, with the call originator transmitting at 1,070 or 1,270 Hz and the answering modem transmitting at 2,025 or 2,225 Hz. The readily available 103A2 gave an important boost to the use of remote low-speed terminals such as the Teletype Model 33 ASR and KSR, AT&T reduced modem costs by introducing the originate-only 113D and the answer-only 113B/C modems. For many years, the Bell System maintained a monopoly on the use of its phone lines, however, the seminal Hush-a-Phone v. FCC case of 1956 concluded it was within the FCCs jurisdiction to regulate the operation of the Bell System. The FCC found that as long as a device was not electronically attached to the system and this led to a number of devices that mechanically connected to the phone through a standard handset. Since most handsets were supplied by Western Electric and thus of a standard design and this type of connection was used for many devices, such as answering machines. Acoustically coupled Bell 103A-compatible 300 bit/s modems were common during the 1970s, well-known models included the Novation CAT and the Anderson-Jacobson, the latter spun off from an in-house project at Stanford Research Institute. An even lower-cost option was the Pennywhistle modem, designed to be built using parts from electronics scrap, in December 1972, Vadic introduced the VA3400, notable for full-duplex operation at 1,200 bit/s over the phone network. Like the 103A, it used different frequency bands for transmit, in November 1976, AT&T introduced the 212A modem to compete with Vadic
22.
Fast Ethernet
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In computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s. Of the Fast Ethernet standards, 100BASE-TX is by far the most common, Fast Ethernet was introduced in 1995 as the IEEE802. 3u standard and remained the fastest version of Ethernet for three years before the introduction of Gigabit Ethernet. The acronym GE/FE is sometimes used for supporting both standards. Fast Ethernet is an extension of the 10-megabit Ethernet standard and it runs on UTP data or optical fiber cable in a star wired bus topology, similar to 10BASE-T where all cables are attached to a hub. Fast Ethernet devices are backward compatible with existing 10BASE-T systems. Fast Ethernet is sometimes referred to as 100BASE-X, where X is a placeholder for the FX, the standard specifies the use of CSMA/CD for media access control. A full-duplex mode is also specified and in all modern networks use Ethernet switches. The 100 in the type designation refers to the transmission speed of 100 Mbit/s. The letter following the dash refers to the medium that carries the signal. A Fast Ethernet adapter can be divided into a media access controller, which deals with the higher-level issues of medium availability. The MAC may be linked to the PHY by a four-bit 25 MHz synchronous parallel interface known as a media-independent interface, in rare cases the MII may be an external connection but is usually a connection between ICs in a network adapter or even within a single IC. The specs are based on the assumption that the interface between MAC and PHY will be a MII but they do not require it. Repeaters may use the MII to connect to multiple PHYs for their different interfaces, the MII fixes the theoretical maximum data bit rate for all versions of Fast Ethernet to 100 Mbit/s. 100BASE-T is any of several Fast Ethernet standards for twisted pair cables, including, 100BASE-TX, 100BASE-T4, the segment length for a 100BASE-T cable is limited to 100 metres. All are or were standards under IEEE802.3, almost all 100BASE-T installations are 100BASE-TX. In the early days of Fast Ethernet, much vendor advertising centered on claims by competing standards that said vendors standards will work better with existing cables than other standards. Thus most networks had to be rewired for 100 Megabit speed whether or not there had supposedly been CAT3 or CAT5 cable runs, 100BASE-TX is the predominant form of Fast Ethernet, and runs over two wire-pairs inside a category 5 or above cable. Like 10BASE-T, the pairs in a standard connection are terminated on pins 1,2,3 and 6
23.
Transmission medium
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A transmission medium is a material substance that can propagate energy waves. For example, the medium for sounds is usually air. The absence of a medium in vacuum may also constitute a transmission medium for electromagnetic waves such as light. The term transmission medium also refers to a device that employs the material substance to transmit or guide waves. Thus, a fiber or a copper cable is a transmission medium. Not only this but also is able to guide the transmission of networks, electromagnetic radiation can be transmitted through an optical medium, such as optical fiber, or through twisted pair wires, coaxial cable, or dielectric-slab waveguides. It may also pass through any material that is transparent to the specific wavelength, such as water, air, glass. Sound is, by definition, the vibration of matter, so it requires a medium for transmission, as do other kinds of mechanical waves. Historically, science incorporated various aether theories to explain the transmission medium, however, it is now known that electromagnetic waves do not require a physical transmission medium, and so can travel through the vacuum of free space. Regions of the vacuum can become conductive for electrical conduction through the presence of free electrons, holes. Transmission and reception of data is performed in four steps, many transmission media are used as communications channel. Wireless —transmission and reception are achieved by means of an antenna, one of the most common physical medias used in networking is copper wire. Copper wire to carry signals to long distances using relatively low amounts of power, the unshielded twisted pair is eight strands of copper wire, organized into four pairs. Another example of a medium is optical fiber, which has emerged as the most commonly used transmission medium for long-distance communications. Optical fiber is a strand of glass that guides light along its length. Four major factors favor optical fiber over copper- data rates, distance, installation, optical fiber can carry huge amounts of data compared to copper. Glass is lighter than copper allowing for less need for specialized heavy-lifting equipment when installing long-distance optical fiber, optical fiber for indoor applications cost approximately a dollar a foot, the same as copper. Multimode and single mode are two types of commonly used optical fiber, multimode fiber uses LEDs as the light source and can carry signals over shorter distances, about 2 kilometers
24.
Medium Attachment Unit
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A Medium Attachment Unit is a transceiver which converts signals on an Ethernet cable to and from Attachment Unit Interface signals. On original 10BASE5 Ethernet, the MAU was typically clamped to the Ethernet cable, for backwards compatibility with equipment which still has external AUI interfaces, MAUs are still available with 10BASE2 or 10BASET connections. The following standard, Fast Ethernet introduces division onto Media Access Controller, some early Fast Ethernet hardware had a physical external MII connectors, functionally similar to AUI connector. Objectives of MAU, Provide the physical means for communication between local network data link entities, Provide a communication channel capable of high bandwidth and low bit error ratio performance. Provide for ease of installation and service, MAU Characteristics, Enables coupling the Physical Layer Signalling by way of the AUI to the explicit baseband coaxial transmission system. Supports message traffic at a rate of 10,100. Provides for driving up to 500m of coaxial cable without the use of a repeater. Permits the DTE to test the MAU and the medium itself, supports system configurations using the CSMA/CD access mechanism defined with baseband signaling. Collision detection and Loop-back functions direct transfer through the MAU and it removes equipment from the network whenever it continuously transmits for periods significantly longer than required for a maximum-length packet, indicating a possible problem with the NIC. The signal quality error test detects silent failures in the circuitry, Link integrity functions detects breaks in the wire pairs. Both Signal quality error test and Link integrity functions assist in fault isolation, two modes of operation, Normal mode, The MAU functions as a direct connection between the baseband medium and the DTE. Data output from the DTE is output to the coaxial trunk medium and this mode is the “normal” mode of operation for the intended message traffic between stations. Monitor mode or Isolated mode, The MAU functions as a connection between the baseband medium and the DTE. Data output from the DTE is suppressed and only data on the coaxial trunk medium is input to the DTE and this mode is for observing message traffic. Receive function The ability to receive serial data bit streams over the baseband medium, collision Presence function The ability to detect the presence of two or more stations concurrent transmissions. Monitor function The ability to inhibit the normal transmit data stream to the medium at the time the normal receive function and collision presence function remain operational. Jabber function The ability to interrupt the transmit function and inhibit an abnormally long output data stream. It removes equipment from the network whenever it continuously transmits for periods longer than required for a maximum-length packet
25.
10BASE2
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As of 2011, IEEE802.3 has deprecated this standard for new installations. The name 10BASE2 is derived from several characteristics of the physical medium, the 10 comes from the transmission speed of 10 Mbit/s. The BASE stands for baseband signalling, and the 2 for a maximum segment length approaching 200 m.10 Mbit/s Ethernet uses Manchester coding. A binary zero is indicated by a low to high transition in the middle of the bit period and this allows the clock to be recovered from the signal. However, the additional transitions double the signal bandwidth, 10BASE2 coax cables have a maximum length of 185 metres. The maximum practical number of nodes that can be connected to a 10BASE2 segment is limited to 30 with a distance of 50 cm. In a 10BASE2 network, each stretch of cable is connected to the using a BNC T-connector. The T-connector must be plugged directly into the network adaptor with no cable in between, as is the case with most other high-speed buses, Ethernet segments have to be terminated with a resistor at each end. Each end of the cable has a 50 ohm resistor attached, typically this resistor is built into a male BNC and attached to the last device on the bus. This is most commonly connected directly to the T-connector on a workstation though it not technically have to be. A few devices such as Digitals DEMPR and DESPR have a built-in terminator, if termination is missing, or if there is a break in the cable, the AC signal on the bus is reflected, rather than dissipated, when it reaches the end. This reflected signal is indistinguishable from a collision, so no communication can take place, when wiring a 10BASE2 network, special care has to be taken to ensure that cables are properly connected to all T-connectors, and appropriate terminators are installed. One, and only one, terminator must be connected to ground via a ground wire, bad contacts or shorts are especially difficult to diagnose, though a time-domain reflectometer will find most problems quickly. A failure at any point of the network cabling tends to prevent all communications, for this reason, 10BASE2 networks can be difficult to maintain and were often replaced by 10BASE-T networks, which also provided a good upgrade path to 100BASE-TX. An alternative, more reliable connection was established by the introduction of EAD sockets, there were proprietary wallport/cable systems that claimed to avoid these problems but these never became widespread, possibly due to a lack of standardization. 10BASE2 systems do have a number of advantages over 10BASE-T, no hub is required as with 10BASE-T, so the hardware cost is minimal, and wiring can be particularly easy since only a single wire run is needed, which can be sourced from the nearest computer. These characteristics mean that 10BASE2 is ideal for a network of two or three machines, perhaps in a home where easily concealed wiring may be an advantage. For a larger complex office network, the difficulties of tracing poor connections make it impractical, unfortunately for 10BASE2, by the time multiple home computer networks became common, the format had already been practically superseded
26.
10BASE5
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10BASE5 was the first commercially available variant of Ethernet. 10BASE5 uses a thick and stiff coaxial cable up to 500 metres in length, up to 100 stations can be connected to the cable using vampire taps and share a single collision domain with 10 Mbit/s of bandwidth shared among them. The system is difficult to install and maintain, as of 2003, IEEE802.3 has deprecated this standard for new installations. The name 10BASE5 is derived from several characteristics of the physical medium, the 10 refers to its transmission speed of 10 Mbit/s. The BASE is short for baseband signalling, and the 5 stands for the segment length of 500 metres. For its physical layer 10BASE5 uses cable similar to RG-8/U coaxial cable and this is a stiff,0. 375-inch diameter cable with an impedance of 50 ohms, a solid center conductor, a foam insulating filler, a shielding braid, and an outer jacket. The outer jacket is often yellow-to-orange fluorinated ethylene propylene so it often is called yellow cable, orange hose, 10BASE5 coaxial cables had a maximum length of 500 metres. Up to 100 nodes could be connected to a 10BASE5 segment, transceiver nodes can be connected to cable segments with N connectors, or via a vampire tap, which allows new nodes to be added while existing connections are live. Transceivers should be installed only at precise 2. 5-metre intervals and this distance was chosen to not correspond to the wavelength of the signal, this ensures that the reflections from multiple taps are not in phase. These suitable points are marked on the cable with black bands, the cable is required to be one continuous run, T-connections are not allowed. As is the case with most other high-speed buses, segments must be terminated at each end, for coaxial-cable-based Ethernet, each end of the cable has a 50 ohm resistor attached. Typically this resistor is built into a male N connector and attached to the end of the cable just past the last device. With termination missing, or if there is a break in the cable and this reflected signal is indistinguishable from a collision, and prevents communication. Adding new stations to network is complicated by the need to pierce the cable. The cable is stiff and difficult to bend around corners, one improper connection could take down the whole network and finding the source of the trouble is difficult.3 or later
27.
Ethernet
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Ethernet /ˈiːθərnɛt/ is a family of computer networking technologies commonly used in local area networks, metropolitan area networks and wide area networks. It was commercially introduced in 1980 and first standardized in 1983 as IEEE802.3, over time, Ethernet has largely replaced competing wired LAN technologies such as token ring, FDDI and ARCNET. The original 10BASE5 Ethernet uses coaxial cable as a medium, while the newer Ethernet variants use twisted pair. Over the course of its history, Ethernet data transfer rates have increased from the original 2.94 megabits per second to the latest 100 gigabits per second. The Ethernet standards comprise several wiring and signaling variants of the OSI physical layer in use with Ethernet, systems communicating over Ethernet divide a stream of data into shorter pieces called frames. As per the OSI model, Ethernet provides services up to, since its commercial release, Ethernet has retained a good degree of backward compatibility. Features such as the 48-bit MAC address and Ethernet frame format have influenced other networking protocols, the primary alternative for some uses of contemporary LANs is Wi-Fi, a wireless protocol standardized as IEEE802.11. Ethernet was developed at Xerox PARC between 1973 and 1974 and it was inspired by ALOHAnet, which Robert Metcalfe had studied as part of his PhD dissertation. In 1975, Xerox filed a patent application listing Metcalfe, David Boggs, Chuck Thacker, in 1976, after the system was deployed at PARC, Metcalfe and Boggs published a seminal paper. Metcalfe left Xerox in June 1979 to form 3Com and he convinced Digital Equipment Corporation, Intel, and Xerox to work together to promote Ethernet as a standard. The so-called DIX standard, for Digital/Intel/Xerox, specified 10 Mbit/s Ethernet, with 48-bit destination and source addresses and it was published on September 30,1980 as The Ethernet, A Local Area Network. Data Link Layer and Physical Layer Specifications, version 2 was published in November,1982 and defines what has become known as Ethernet II. Formal standardization efforts proceeded at the time and resulted in the publication of IEEE802.3 on June 23,1983. Ethernet initially competed with two largely proprietary systems, Token Ring and Token Bus, in the process, 3Com became a major company. 3Com shipped its first 10 Mbit/s Ethernet 3C100 NIC in March 1981, an Ethernet adapter card for the IBM PC was released in 1982, and, by 1985, 3Com had sold 100,000. Parallel port based Ethernet adapters were produced for a time, with drivers for DOS, by the early 1990s, Ethernet became so prevalent that it was a must-have feature for modern computers, and Ethernet ports began to appear on some PCs and most workstations. This process was sped up with the introduction of 10BASE-T and its relatively small modular connector. Since then, Ethernet technology has evolved to meet new bandwidth, in addition to computers, Ethernet is now used to interconnect appliances and other personal devices
28.
Optical fiber
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An optical fiber or optical fibre is a flexible, transparent fiber made by drawing glass or plastic to a diameter slightly thicker than that of a human hair. Fibers are also used for illumination, and are wrapped in bundles so that they may be used to carry images, thus allowing viewing in confined spaces, as in the case of a fiberscope. Specially designed fibers are used for a variety of other applications, some of them being fiber optic sensors. Optical fibers typically include a transparent core surrounded by a transparent cladding material with an index of refraction. Light is kept in the core by the phenomenon of internal reflection which causes the fiber to act as a waveguide. Fibers that support many propagation paths or transverse modes are called multi-mode fibers, multi-mode fibers generally have a wider core diameter and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1,000 meters, being able to join optical fibers with low loss is important in fiber optic communication. This is more complex than joining electrical wire or cable and involves careful cleaving of the fibers, precise alignment of the cores. For applications that demand a permanent connection a fusion splice is common, in this technique, an electric arc is used to melt the ends of the fibers together. Another common technique is a splice, where the ends of the fibers are held in contact by mechanical force. Temporary or semi-permanent connections are made by means of specialized optical fiber connectors, the field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. The term was coined by Indian physicist Narinder Singh Kapany who is acknowledged as the father of fiber optics. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon, John Tyndall included a demonstration of it in his public lectures in London,12 years later. When the ray passes from water to air it is bent from the perpendicular. If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the angle which marks the limit where total reflection begins is called the limiting angle of the medium. For water this angle is 48°27′, for flint glass it is 38°41′, unpigmented human hairs have also been shown to act as an optical fiber. Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth century, image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. The principle was first used for medical examinations by Heinrich Lamm in the following decade
29.
Gigabit Ethernet
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In computer networking, Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second, as defined by the IEEE802. 3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks, the cables and equipment are very similar to previous standards and have been very common and economical since 2010. Ethernet was the result of the research done at Xerox PARC in the early 1970s, Ethernet later evolved into a widely implemented physical and link layer protocol. Fast Ethernet increased speed from 10 to 100 megabits per second, Gigabit Ethernet was the next iteration, increasing the speed to 1000 Mbit/s. The initial standard for Gigabit Ethernet was produced by the IEEE in June 1998 as IEEE802. 3z,802. 3z is commonly referred to as 1000BASE-X, where -X refers to either -CX, -SX, -LX, or -ZX. For the history behind the X see Fast Ethernet, IEEE802. 3ab, ratified in 1999, defines Gigabit Ethernet transmission over unshielded twisted pair category 5, 5e or 6 cabling, and became known as 1000BASE-T. With the ratification of 802. 3ab, Gigabit Ethernet became a desktop technology as organizations could use their existing copper cabling infrastructure, IEEE802. 3ah, ratified in 2004 added two more gigabit fiber standards, 1000BASE-LX10 and 1000BASE-BX10. This was part of a group of protocols known as Ethernet in the First Mile. Initially, Gigabit Ethernet was deployed in high-capacity backbone network links, in 2000, Apples Power Mac G4 and PowerBook G4 were the first mass-produced personal computers featuring the 1000BASE-T connection. It quickly became a feature in many other computers. There are five physical layer standards for Gigabit Ethernet using optical fiber, twisted pair cable and these standards use 8b/10b encoding, which inflates the line rate by 25%, from 1000 Mbit/s to 1250 Mbit/s, to ensure a DC balanced signal. The symbols are sent using NRZ. Optical fiber transceivers are most often implemented as modules in SFP form or GBIC on older devices. IEEE802. 3ab, which defines the widely used 1000BASE-T interface type, uses a different encoding scheme in order to keep the rate as low as possible. IEEE802. 3ap defines Ethernet Operation over Electrical Backplanes at different speeds, Ethernet in the First Mile later added 1000BASE-LX10 and -BX10. 1000BASE-CX is a standard for Gigabit Ethernet connections with maximum distances of 25 meters using balanced shielded twisted pair. The short segment length is due to high signal transmission rate. 1000BASE-KX is part of the IEEE802. 3ap standard for Ethernet Operation over Electrical Backplanes and this standard defines one to four lanes of backplane links, one RX and one TX differential pair per lane, at link bandwidth ranging from 100Mbit to 10Gbit per second
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10 Gigabit Ethernet
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10 Gigabit Ethernet is a group of computer networking technologies for transmitting Ethernet frames at a rate of 10 gigabits per second. It was first defined by the IEEE802. 3ae-2002 standard, half duplex operation and repeater hubs do not exist in 10GbE. Like previous versions of Ethernet, 10GbE can use either copper or fiber cabling, however, because of its bandwidth requirements, higher-grade copper cables are required, category 6a or Class F/Category 7 cables for lengths up to 100 meters. The 10 Gigabit Ethernet standard encompasses a number of different physical layer standards, a networking device, such as a switch or a network interface controller may have different PHY types through pluggable PHY modules, such as those based on SFP+. At the time that the 10 Gigabit Ethernet standard was developed, the WAN PHY encapsulates Ethernet packets in SONET OC-192c frames and operates at a slightly slower data-rate than the local area network PHY. Over the years the Institute of Electrical and Electronics Engineers 802.3 working group has published several standards relating to 10GbE, to implement different 10GbE physical layer standards, many interfaces consist of a standard socket into which different PHY modules may be plugged. Physical layer modules are not specified in a standards body. Relevant MSAs for 10GbE include XENPAK, XFP and SFP+, when choosing a PHY module, a designer considers cost, reach, media type, power consumption, and size. A single point-to-point link can have different MSA pluggable formats on either end as long as the 10GbE optical or copper port type inside the pluggable is identical, XENPAK was the first MSA for 10GE and had the largest form factor. X2 and XPAK were later competing standards with smaller form factors, X2 and XPAK have not been as successful in the market as XENPAK. XFP came after X2 and XPAK and it is also smaller, the newest module standard is the enhanced small form-factor pluggable transceiver, generally called SFP+. Based on the small form-factor pluggable transceiver and developed by the ANSI T11 fibre channel group, it is smaller still, SFP+ has become the most popular socket on 10GE systems. SFP+ modules do only optical to electrical conversion, no clock and data recovery, SFP+ modules share a common physical form factor with legacy SFP modules, allowing higher port density than XFP and the re-use of existing designs for 24 or 48 ports in a 19 rack width blade. Optical modules are connected to a host by either a XAUI, XENPAK, X2, and XPAK modules use XAUI to connect to their hosts. XAUI uses a data channel and is specified in IEEE802.3 Clause 48. XFP modules use a XFI interface and SFP+ modules use an SFI interface, XFI and SFI use a single lane data channel and the 64b/66b encoding specified in IEEE802.3 Clause 49. SFP+ modules can further be grouped into two types of host interfaces, linear or limiting, limiting modules are preferred except when using old fiber infrastructure which requires the use of the linear interface provided by 10GBASE-LRM modules. There are two classifications for optical fiber, single-mode and multi-mode, in SMF light follows a single path through the fiber while in MMF it takes multiple paths resulting in differential mode delay
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100 Gigabit Ethernet
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40 Gigabit Ethernet and 100 Gigabit Ethernet are groups of computer networking technologies for transmitting Ethernet frames at rates of 40 and 100 gigabits per second, respectively. The technology was first defined by the IEEE802. 3ba-2010 standard and later by the 802. 3bg-2011,802. 3bj-2014, the standards define numerous port types with different optical and electrical interfaces and different numbers of optical fiber strands per port. Short distances over twinaxial cable are supported, 40GBASE-T uses twisted pair cabling for 40 Gbit/s over up to 30 m. On July 18,2006, a call for interest for a High Speed Study Group to investigate new standards for high speed Ethernet was held at the IEEE802.3 plenary meeting in San Diego. The first 802.3 HSSG study group meeting was held in September 2006, in June 2007, a trade group called Road to 100G was formed after the NXTcomm trade show in Chicago. The project is to provide for the interconnection of equipment satisfying the requirements of the intended applications. The 802. 3ba task force met for the first time in January 2008 and this standard was approved at the June 2010 IEEE Standards Board meeting under the name IEEE Std 802. 3ba-2010. On June 17,2010, the IEEE802. 3ba standard was approved In March 2011 the IEEE802. 3bg standard was approved, on September 10,2011, the P802. 3bj 100 Gbit/s Backplane and Copper Cable task force was approved. The scope of project is to specify additions to and appropriate modifications of IEEE Std 802. On May 10,2013, the P802. 3bm 40 Gbit/s and 100 Gbit/s Fiber Optic Task Force was approved and this project is to specify additions to and appropriate modifications of IEEE Std 802. In addition, to add 40 Gb/s Physical Layer specifications and management parameters for operation on extended reach single-mode fiber optic cables, also on May 10,2013, the P802. 3bq 40GBASE-T Task Force was approved. On June 12,2014, the IEEE802. 3bj standard was approved, on February 16,2015, the IEEE802. 3bm standard was approved. On May 12,2016, the IEEE P802. 3cd Task Force started working to define next generation two-lane 100 Gbit/s PHY, the IEEE802.3 working group is concerned with the maintenance and extension of the Ethernet data communications standard. Additions to the 802.3 standard are performed by forces which are designated by one or two letters. For example, the 802. 3z task force drafted the original Gigabit Ethernet standard,802. 3ba is the designation given to the higher speed Ethernet task force which completed its work to modify the 802.3 standard to support speeds higher than 10 Gbit/s in 2010. The speeds chosen by 802. 3ba were 40 and 100 Gbit/s to support both end-point and link aggregation needs and this was the first time two different Ethernet speeds were specified in a single standard. The decision to include both speeds came from pressure to support the 40 Gbit/s rate for local applications and the 100 Gbit/s rate for internet backbones. The standard was announced in July 2007 and was ratified on June 17,2010, the 40/100 Gigabit Ethernet standards encompass a number of different Ethernet physical layer specifications
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Gigabit interface converter
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A gigabit interface converter is a standard for transceivers, commonly used with Gigabit Ethernet and fibre channel in the 2000s. A variation of the GBIC called the small form-factor pluggable transceiver, also known as mini-GBIC, has the same functionality, announced in 2001, it largely made the GBIC obsolete. The appeal of the GBIC standard in networking equipment, as opposed to fixed physical interface configurations, is its flexibility. Where multiple different optical technologies are in use, an administrator can purchase GBICs as needed, not in advance and this lowers the cost of the base system and gives the administrator far more flexibility. On the other hand, if a switch will mostly have one port type purchasing a switch with that type built in will be cheaper. The GBIC standard is non-proprietary and is defined by the Small Form Factor committee in document number 8053i, the first publication of the proposal was in November 1995. A few corrections and additions were made through September 2000, robert Snively of Brocade Communications was technical editor. Original contributors were AMP Incorporated, Compaq Computers, Sun Microsystems, and Vixel Corporation
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Small form-factor pluggable transceiver
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The small form-factor pluggable is a compact, hot-pluggable transceiver used for both telecommunication and data communications applications. The form factor and electrical interface are specified by an agreement under the auspices of the SFF Committee. It is an industry format jointly developed and supported by many network component vendors. The SFP interfaces a network device motherboard to a fiber optic or copper networking cable, SFP transceivers are designed to support SONET, gigabit Ethernet, Fibre Channel, and other communications standards. Due to its size, SFP obsolesces the formerly ubiquitous gigabit interface converter. In fact, no device with this name has ever been defined in the MSAs, transceivers are most often designated by the standard transmission speed on the medium, but sometimes they are labeled with their nominal Ethernet speed or a higher speed the manufacturer specifies. Not compatible with SX or 100BASE-FX, based on LX but engineered to work with a multi-mode fiber using a standard multi-mode patch cable rather than a mode-conditioning cable commonly used to adapt LX to multi-mode. Coupled with CWDM, these double the density of fiber links. They are not compatible with Fiber channel or SONET, unlike non-SFP, copper 1000BASE-T ports integrated into most routers and switches, 1000BASE-T SFPs usually cannot operate at 100BASE-TX speeds. 100 Mbit/s copper and optical - some vendors have shipped 100 Mbit/s limited SFPs for fiber to the home applications and these are relatively uncommon and can be easily confused with 1 Gbit/s SFPs. The enhanced small form-factor pluggable is a version of the SFP that supports data rates up to 16 Gbit/s. The SFP+ specification was first published on May 9,2006, SFP+ supports 8 Gbit/s Fibre Channel,10 Gigabit Ethernet and Optical Transport Network standard OTU2. It is an industry format supported by many network component vendors. 10 Gbit/s SFP+ modules are exactly the same dimensions as regular SFPs, allowing the equipment manufacturer to re-use existing physical designs for 24 and 48-port switches, although the SFP+ standard does not include mention of 16G Fibre Channel it can be used at this speed. Besides the data rate, the big difference between 8G Fibre Channel and 16G Fibre Channel is the encoding method, 64b/66b encoding used for 16G is a more efficient encoding mechanism than 8b/10b used for 8G, and allows for the data rate to double without doubling the line rate. The result is the 14.025 Gbit/s line rate for 16G Fibre Channel, in comparison to earlier XENPAK or XFP modules, SFP+ modules leave more circuitry to be implemented on the host board instead of inside the module. Through the use of an active adapter, SFP+ modules may be used in older equipment with XENPAK ports. SFP+ modules can be described as limiting or linear types, this describes the functionality of the inbuilt electronics, limiting SFP+ modules include a signal amplifier to re-shape the received signal whereas linear ones do not
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QSFP
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The Quad Small Form-factor Pluggable is a compact, hot-pluggable transceiver used for data communications applications. The form factor and electrical interface are specified by an agreement under the auspices of the Small Form Factor Committee. It interfaces networking hardware to a fiber cable or active or passive electrical copper connection. It is an industry format jointly developed and supported by many network component vendors, the format specification is evolving to enable higher data rates, as of May 2013, highest possible rate is 4x28 Gbit/s. QSFP modules are available in several different categories, The original QSFP document specified four channels carrying Gigabit Ethernet, 4GFC. QSFP+ is an evolution of QSFP to support four 10 Gbit/sec channels carrying 10 Gigabit Ethernet, 10GFC FiberChannel, the 4 channels can also be combined into a single 40 Gigabit Ethernet link. The QSFP14 standard is designed to carry FDR InfiniBand and SAS-3, the QSFP28 standard is designed to carry 100 Gigabit Ethernet or EDR InfiniBand. This transceiver type is used with direct-attach breakout cables to adapt a single 100GbE port to four independent 25 gigabit ethernet ports. Sometimes this transceiver type is referred to as QSFP100 or 100G QSFP for sake of simplicity. QSFP has 38 pins with 4 high-speed TX pairs and 4 high-speed RX pairs, C Form-factor Pluggable CXP OSFP transceiver slightly larger 400GbE transceiver standard Small form-factor pluggable transceiver SFF Committee
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XFP transceiver
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The XFP is a standard for transceivers for high-speed computer network and telecommunication links that use optical fiber. It was defined by an group in 2002, along with its interface to other electrical components. XFP is a larger form factor than the popular small form-factor pluggable transceiver, SFP. XFP modules are hot-swappable and protocol-independent and they typically operate at near-infrared wavelengths of 850 nm,1310 nm or 1550 nm. They can operate over a wavelength or use dense wavelength-division multiplexing techniques. They include digital diagnostics that provide management that were added to the SFF-8472 standard, XFP modules use an LC fiber connector type to achieve higher density. The XFP specification was developed by the XFP Multi Source Agreement Group and it is an informal agreement of an industry group, not officially endorsed by any standards body. The first preliminary specification was published on March 27,2002, the first public release was on July 19,2002. It was adopted on March 3,2003, and updated with minor updates through August 31,2005, the chair of the XFP group was Robert Snively of Brocade Communications Systems, and technical editor was Ali Ghiasi of Broadcom. The organizations web site was maintained until 2009, the XFI electrical interface specification was a 10 gigabit per second chip-to-chip electrical interface specification defined as part of the XFP multi-source agreement. It was also developed by the XFP MSA group, XFI is sometimes pronounced as X F I and other times as ziffie. XFI provides a single lane running at 10.3125 Gbit/s when using a 64B/66B encoding scheme, a serializer/deserializer is often used to convert between XFI and a wider interface such as XAUI that has four lanes running at 3.125 Gbit/s using 8B/10B encoding. The physical dimensions of the XFP transceiver are slightly larger than the original small form-factor pluggable transceiver, one of the reasons for the increase in size is to allow for on-board heat sinks for more cooling. Some vendors supported both, or the XENPAK follow-ons called XPAK and X2
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Modular connector
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A modular connector is an electrical connector that was originally designed for use in telephone wiring, but has since been used for many other purposes. Many applications that used a bulkier, more expensive connector have converted to modular connectors. Probably the most well known applications of modular connectors are for telephone jacks and for Ethernet jacks, Modular connectors were originally used in the Registration Interface system, mandated by the Federal Communications Commission in 1976 in which they became known as registered jacks. The registered jack specifications define the wiring patterns of the jacks, instead, these latter aspects are covered by ISO standard 8877, first used in ISDN systems. TIA/EIA-568 is a standard for data circuits wired on modular connectors, other systems exist for assigning signals to modular connectors, physical interchangeability of plugs and jacks does not ensure interoperation, nor protection from electrical damage to circuits. For example, modular cables and connectors have used to supply low-voltage AC or DC power. Modular connectors also go by the names modular phone jack/plug, RJ connector, the term modular connector arose from its original use in a novel system of cabling designed to make telephone equipment more modular. This includes the 4P4C handset connector, a very popular use of 8P8C today is Ethernet over twisted pair, and that may be the most well known context in which the name RJ45 is known, even though it has nothing to do with the RJ45 standard. Likewise, the 4P4C connector is sometimes called RJ9 or RJ22, Modular connectors were originally developed and patented by General Cable Corp in 1974. They replaced the hard-wired connections on most Western Electric telephones around 1976, at the same time, they began to replace screw terminals and larger 3 and 4 pin telephone jacks in buildings. Modular connectors have gender, plugs are considered to be male, while jacks or sockets are considered to be female, plugs are used to terminate loose cables and cords, while jacks are used for fixed locations on surfaces such as walls and panels, and on equipment. Other than telephone extension cables, cables with a plug on one end. Instead, cables are connected using an adapter, which consists of two female jacks wired back-to-back. Modular connectors are designed to latch together, a spring-loaded tab on the plug snaps into a jack so that the plug cannot be pulled out. To remove the plug, the latching tab must be depressed, the standard and most common way to install a jack in a wall or panel is with the tab side down. This usually makes it easier to operate the tab when removing the plug, because the person grabs the plug with thumb on top, the modular connector suffers from a design flaw or weakness however, as the fragile latching tab easily snags on other cables and breaks off. When this happens, the connector is still functional, but the crucial latching feature is lost, some higher quality cables have a flexible sleeve called a boot over the plug, or a special tab design, to prevent this. These cables are marketed as snagless
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Electrical connector
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An electrical connector, is an electro-mechanical device used to join electrical terminations and create an electrical circuit. Electrical connectors consist of plugs and jacks, the connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or devices. An adapter can be used to bring together dissimilar connectors. There are hundreds of types of electrical connectors, connectors may join two lengths of flexible copper wire or cable, or connect a wire or cable to an electrical terminal. In computing, a connector can also be known as a physical interface. Cable glands, known as cable connectors in the US, connect wires to devices rather than electrically and are distinct from quick-disconnects performing the latter. It is usually desirable for a connector to be easy to visually, rapid to assemble, require only simple tooling. In some cases an equipment manufacturer might choose a connector specifically because it is not compatible with those other sources. No single connector has all the properties, the proliferation of types is a reflection of differing requirements. Fretting is a failure mode in electrical connectors that have not been specifically designed to prevent it. Many connectors are keyed, with some mechanical component which prevents mating except with a correctly oriented matching connector, some connector housings are designed with locking mechanisms to prevent inadvertent disconnection or poor environmental sealing. Locking mechanism designs include locking levers of various sorts, screw locking, a terminal is a simple type of electrical connector that connects two or more wires to a single connection point. Wire nuts are another type of single point connector, terminal blocks provide a convenient means of connecting individual electrical wires without a splice or physically joining the ends. They are usually used to connect wiring among various items of equipment within an enclosure or to make connections among individually enclosed items. Since terminal blocks are available for a wide range of wire sizes and terminal quantity. One type of terminal block accepts wires that are prepared only by removing a short length of insulation from the end, another type accepts wires that have ring or spade terminal lugs crimped onto the wires. Printed circuit board mounted terminal blocks allow individual wires to be connected to the circuit board, a general type of connector that simply screws or clamps bare wire to a post, such connectors are frequently used in electronic test equipment and audio. Many, but not all binding posts will also accept a banana connector plug, since stripping the insulation from wires is time-consuming, many connectors intended for rapid assembly use insulation-displacement connectors so that insulation need not be removed from the wire
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Duplex (telecommunications)
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A duplex communication system requires a pair of channels/frequencies hence the term duplex meaning two parts. The two channels are defined as uplink/downlink or reverse/forward, in a full-duplex system simultaneous transmission/reception is available, i. e. One can transmit and receive simultaneously, in a half-duplex system, each party can communicate with the other but not simultaneously, the communication is one direction at a time. Half duplex systems utilize separate channels for uplink and downlink, i. e. a transmit, in a half duplex communications system one user is allowed to transmit on the uplink channel at a time. The transmitted uplink signal is frequency translated via a radio/repeater to the downlink receive frequency which is received by all other radios tuned to the downlink/receive frequency. A half-duplex system is defined as system which operates two, hence duplex, dedicated uplink/downlink channels/frequencies. In a half duplex system a single path is provided for uplink, all uplink messages are broadcast via the downlink channel to all users simultaneously via a repeater which performs uplink to downlink channel/frequency translation. All cellular and land line PSTNs and PDSNs are full duplex systems, all full duplex systems require a channel/frequency translator via a radio/repeater. This is required in order to translate the uplink/transmit transmission from one to the downlink/receive channel/frequency of user two. Full duplex systems are one to one private systems unlike half duplex systems which broadcast to all users and this effectively makes the cable itself a collision-free environment and doubles the maximum total transmission capacity supported by each Ethernet connection. Time-division duplexing is commonly referred to as simplex communications, a single channel/frequency is employed for bidirectional communications. The term simplex communication as applied to TDM single channel systems predates the term TDD by at least 80 years, frequency-division duplexing as with any other duplex system is defined by two channel/frequency simultaneous communication. A channel/frequency pair are assigned to individual user on the system. An FDD system requires frequency translation from user 1 uplink/reverse frequency to user 2 downlink/forward frequency, full-duplex audio systems like telephones can create echo, which needs to be removed. Echo occurs when the coming out of the speaker, originating from the far end. The sound then reappears at the source end, but delayed. This feedback path may be acoustic, through the air, or it may be mechanically coupled, echo cancellation is a signal-processing operation that subtracts the far-end signal from the microphone signal before it is sent back over the network. Echo cancellation is important to the V.32, V.34, V.56, echo cancelers are available as both software and hardware implementations
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General Services Administration
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The General Services Administration is an independent agency of the United States government, established in 1949 to help manage and support the basic functioning of federal agencies. GSA employs about 12,000 federal workers and has an operating budget of roughly $26.3 billion. GSA oversees $66 billion of procurement annually and it contributes to the management of about $500 billion in U. S. federal property, divided chiefly among 8,300 owned and leased buildings and a 210,000 vehicle motor pool. GSAs business lines include the Federal Acquisition Service, the Public Buildings Service, the GSA is member of the Procurement G6, an informal group leading the use of framework agreements and e-procurement instruments in public procurement. In 1947 President Harry Truman asked former President Herbert Hoover to lead what became known as the Hoover Commission to make recommendations to reorganize the operations of the federal government, one of the recommendations of the commission was the establishment of an Office of the General Services. This proposed office would combine the responsibilities of the following organizations, General Jess Larson, Administrator of the War Assets Administration, was named GSAs first Administrator. The first job awaiting Administrator Larson and the newly formed GSA was a renovation of the White House. The structure had fallen into such a state of disrepair by 1949 that one inspector of the time said the structure was standing “purely from habit. Everything, except the four walls without a roof, was stripped down. GSA completed the renovation in 1952, GSA headquarters, located at Eighteenth and F Streets, NW, was U. S. General Services Administration Building listed on the National Register of Historic Places in 1986 as Interior Department Offices, in 1960, GSA created the Federal Telecommunications System, a government-wide intercity telephone system. In 1970, the Nixon administration created the Consumer Product Information Coordinating Center, the Federal Buildings Fund was initiated in 1974, which allowed the GSA to issue rent bills to federal agencies. In 1972, the GSA established the Automated Data and Telecommunications Service, in 1973, the GSA created the Office of Federal Management Policy. GSA’s Office of Acquisition Policy centralized procurement policy in 1978, in 1984, GSA introduced the federal government to the use of charge cards, known as the GMA SmartPay system. The National Archives and Records Administration was spun off into an independent agency in 1985, the same year, the GSA began to provide governmentwide policy oversight and guidance for federal real property management as a result of an Executive Order signed by President Ronald Reagan. In 2003, the Federal Protective Service was moved to the Department of Homeland Security, in 2005, GSA reorganized to merge the Federal Supply Service and Federal Technology Service business lines into the Federal Acquisition Service. On April 3,2009, President Barack Obama nominated Martha N. Johnson to serve as the GSA Administrator, after a 9-month delay, the United States Senate confirmed her nomination on February 4,2010. In July 1991, GSA contractors began the excavation of what is now the Ted Weiss Federal Building in New York City, when initial excavation disturbed burials, destroying skeletons and artifacts, GSA sent archaeologists to excavate—but hid their findings from the public
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MIL-STD-188
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MIL-STD-188 is a series of U. S. military standards relating to telecommunications. S. Department of Defense looked to develop a series of standards that would alleviate the problem, … systems developed for use by U. S. forces are considered to be for joint use. The MIL-STD-188 standards were created to address telecommunication design parameters based on proven technologies, to ensure interoperability, DISA made these standards mandatory for use in all new DoD systems and equipment, or major upgrades. The mandatory use of standards will aid significantly in achieving standardization and result in improvements in availability, maintainability, reliability. This, in turn, will enhance lifecycle configuration management and logistic support with subsequent reductions in life cycle costs, in line with a decision by the Joint Chiefs of Staff, these standards are published in the MIL-STD-188 series of documents. The MIL-STD-188 series standards are encompassed by the DoD’s Joint Technical Architecture, for any DoD Agency to get a waiver to receive an item that deviates from the standards they also must apply to the JSC. Currently the DoD is placing its emphasis on the development of standards for tactical. Note, The following list of documents are those that are presently active, documents with three digit numbers followed by a letter of the alphabet indicate that they are revisions of an older version of that document. According to the DoD the MIL-STD-188-100 series contains technical standards and design objectives which are common to both the long haul and tactical communications systems, database with most MILSTD and DEFSTAN publications
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John Stone Stone
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John Stone Stone was an American mathematician, physicist and inventor. He initially worked in research, followed by influential work developing early radio technology. Despite his often advanced designs, the Stone Telegraph and Telephone Company failed in 1908, Stone was born in Dover village, in Goochland County, Virginia, the son of Charles Pomeroy Stone, an American Civil War Union general and engineer, and Annie Jeannie Stone. After completing his education, in 1890 he began working at the American Bell Telephone Co. in Boston, Massachusetts, in the department of its Research. While there, drawing on the work of Oliver Heaviside, he made a mathematical analysis of the companys development of a long-distance telephone link between New York and Chicago. His later work involved electrical resonance, which he investigated for its potential use in an automatic telephone exchange. In 1892, he attempted to transmit audio using high frequency transmissions. In 1893, he developed a battery system for telephone use, which provided, from a central location. From 1896 to 1906 he also gave a short course of instruction in electrical resonance at the Massachusetts Institute of Technology to graduating classes in physics. His first client was Herman W. Ladd, who was attempting to perfect his Telelocograph system for using radio signals as wireless lighthouses, moreover, unlike most other early radio experimenters, Stone had the mathematical background needed to fully analyze electrical circuits. In late 1900, the Stone Wireless Telegraphy Syndicate was started in Boston, with a funding of $10,000. Stone used his knowledge of electrical tuning to develop a high selectivity approach to reduce the amount of interference caused by static and he also took special care to mathematically analyze transmitter and receiver designs to increase efficiency and reduce losses. In early 1900, he applied for a U. S. patent for his tuning work, in mid-1902 the Stone Telegraph and Telephone Company, also based in Boston, was formed, in order to begin commercial operations. Stone acted as Chief Engineer, and two stations separated by sixteen kilometers were constructed at Cambridge and Lynn, Massachusetts, beginning in 1905, demonstration radiotelegraph stations, using spark transmitters and electrolytic detectors, were installed for evaluation by the U. S. Navy. By the end of 1906, the government had purchased five ship, in 1907 Stone founded, and served as the president of, the Society of Wireless Telegraph Engineers, which was created as an educational resource for his companys employees. In 1906 the company tested a ship-borne direction-finder designed by Stone that, although fairly accurate, proved impractical as it required the entire ship to turn in order to take readings. Operating as an independent concern, Stone found that he could not keep up with the advances in the industry, and in 1908 his company suspended operations. Its assets, including its valuable portfolio of patents, were sold to Lee DeForests Radio Telephone Company, for $10,000 cash, in early 1911, he moved to New York City, once again working as a consultant
This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C" (in support of MIL-STD-188).
This article incorporates