1.
Coaxial
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In geometry, coaxial means that two or more three-dimensional linear forms share a common axis. Thus, it is concentric in three-dimensional, linear forms, a coaxial cable, as a common example, is a three-dimensional linear structure. It has a conductor in the centre, a circumferential outer conductor. The outer conductor is usually sheathed in a protective PVC outer jacket, all these have a common axis. The dimension and material of the conductors and insulation determine the characteristic impedance. In loudspeaker design, coaxial speakers are a system in which the individual driver units radiate sound from the same point or axis
2.
Passband
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A passband is the range of frequencies or wavelengths that can pass through a filter. For example, a radio receiver contains a filter to select the frequency of the desired radio signal out of all the radio waves picked up by its antenna. The passband of a receiver is the range of frequencies it can receive, a bandpass-filtered signal, is known as a bandpass signal, in contrast to a baseband signal. In telecommunications, optics, and acoustics, a passband is the portion of the spectrum that is transmitted by some filtering device. In other words, it is a band of frequencies which passes through some filter or set of filters, the accompanying figure shows a schematic of a waveform being filtered by a bandpass filter consisting of a highpass and a lowpass filter. Radio receivers generally include a tunable band-pass filter with a passband that is enough to accommodate the bandwidth of the radio signal transmitted by a single station. There are two categories of digital communication transmission methods, baseband and passband. In baseband transmission, line coding is utilized, resulting in a train or pulse amplitude modulated signal. This is typically used over non-filtered wires such as fiber optical cables and short-range copper links, for example, V.29, V.35, IEEE802.3, SONET/SDH. In passband transmission, digital methods are employed so that only a limited frequency range is used in some bandpass filtered channel. Passband transmission is utilized in wireless communication and in bandpass filtered channels such as POTS lines. It also allows for frequency-division multiplexing, the digital bit stream is converted first into an equivalent baseband signal, and then to a RF signal. On the receiver side a demodulator is used to detect the signal, a combined equipment for modulation and demodulation is called a modem. In general, there is a relationship between the width of a filters passband and the time required for the filter to respond to new inputs. This is a consequence of the mathematics of Fourier analysis, the limiting frequencies of a passband are defined as those at which the relative intensity or power decreases to a specified fraction of the maximum intensity or power. This decrease in power is often specified to be the half-power points, the difference between the limiting frequencies is called the bandwidth, and is expressed in hertz. The related term bandpass is an adjective that describes a type of filter or filtering process, it is confused with passband. The two words are both words that follow the English rules of formation, the primary meaning is the latter part of the compound
3.
Coaxial cable
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Coaxial cable, or coax, is a type of cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. Many coaxial cables also have an outer sheath or jacket. The term coaxial comes from the conductor and the outer shield sharing a geometric axis. Coaxial cable was invented by English engineer and mathematician Oliver Heaviside, Coaxial cable is used as a transmission line for radio frequency signals. Its applications include feedlines connecting radio transmitters and receivers with their antennas, computer network connections, digital audio and this allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines. Coaxial cable also provides protection of the signal from external electromagnetic interference, the cable is protected by an outer insulating jacket. Normally, the shield is kept at ground potential and a signal carrying voltage is applied to the center conductor, the advantage of coaxial design is that electric and magnetic fields are restricted to the dielectric with little leakage outside the shield. Conversely, electric and magnetic fields outside the cable are largely kept from interfering with signals inside the cable, larger diameter cables and cables with multiple shields have less leakage. Common applications of coaxial cable include video and CATV distribution, RF and microwave transmission, the characteristic impedance of the cable is determined by the dielectric constant of the inner insulator and the radii of the inner and outer conductors. A controlled cable characteristic impedance is important because the source and load impedance should be matched to ensure maximum power transfer, other important properties of coaxial cable include attenuation as a function of frequency, voltage handling capability, and shield quality. Coaxial cable design choices affect physical size, frequency performance, attenuation, power handling capabilities, flexibility, strength, the inner conductor might be solid or stranded, stranded is more flexible. To get better performance, the inner conductor may be silver-plated. Copper-plated steel wire is used as an inner conductor for cable used in the cable TV industry. The insulator surrounding the conductor may be solid plastic, a foam plastic. The properties of control some electrical properties of the cable. A common choice is a solid polyethylene insulator, used in lower-loss cables, solid Teflon is also used as an insulator. Some coaxial lines use air and have spacers to keep the conductor from touching the shield. Many conventional coaxial cables use braided copper wire forming the shield and this allows the cable to be flexible, but it also means there are gaps in the shield layer, and the inner dimension of the shield varies slightly because the braid cannot be flat
4.
Electronics
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Electronics is the science of controlling electrical energy electrically, in which the electrons have a fundamental role. Commonly, electronic devices contain circuitry consisting primarily or exclusively of active semiconductors supplemented with passive elements, the science of electronics is also considered to be a branch of physics and electrical engineering. The ability of electronic devices to act as switches makes digital information processing possible, until 1950 this field was called radio technology because its principal application was the design and theory of radio transmitters, receivers, and vacuum tubes. Today, most electronic devices use semiconductor components to perform electron control and this article focuses on engineering aspects of electronics. Components are generally intended to be connected together, usually by being soldered to a circuit board. Components may be packaged singly, or in more complex groups as integrated circuits, some common electronic components are capacitors, inductors, resistors, diodes, transistors, etc. Components are often categorized as active or passive, vacuum tubes were among the earliest electronic components. They were almost solely responsible for the revolution of the first half of the Twentieth Century. They took electronics from parlor tricks and gave us radio, television, phonographs, radar, long distance telephony and they played a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s. Since that time, solid state devices have all but completely taken over, vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode ray tubes, specialist audio equipment, guitar amplifiers and some microwave devices. The 608 contained more than 3,000 germanium transistors, thomas J. Watson Jr. ordered all future IBM products to use transistors in their design. From that time on transistors were almost exclusively used for computer logic, circuits and components can be divided into two groups, analog and digital. A particular device may consist of circuitry that has one or the other or a mix of the two types, most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a range of voltage or current as opposed to discrete levels as in digital circuits. The number of different analog circuits so far devised is huge, especially because a circuit can be defined as anything from a single component, analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, one rarely finds modern circuits that are entirely analog. These days analog circuitry may use digital or even microprocessor techniques to improve performance and this type of circuit is usually called mixed signal rather than analog or digital. Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation, an example is the comparator which takes in a continuous range of voltage but only outputs one of two levels as in a digital circuit
5.
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
6.
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
7.
Characteristic impedance
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Characteristic impedance is determined by the geometry and materials of the transmission line and, for a uniform line, is not dependent on its length. The SI unit of characteristic impedance is the ohm, the characteristic impedance of a lossless transmission line is purely real, with no reactive component. Energy supplied by a source at one end of such a line is transmitted through the line without being dissipated in the line itself, the characteristic impedance of a transmission line is the ratio of the voltage and current of a wave travelling along the line. When the wave reaches the end of the line, in general, when this wave reaches the source, it adds to the transmitted wave and the ratio of the voltage and current at the input to the line will no longer be the characteristic impedance. This new ratio is called the input impedance, the input impedance of an infinite line is equal to the characteristic impedance since the transmitted wave is never reflected back from the end. This is so there is no reflection on a line terminated in its own characteristic impedance. Although an infinite line is assumed, since all quantities are per unit length, a surge of energy on a finite transmission line will see an impedance of Z0 prior to any reflections arriving, hence surge impedance is an alternative name for characteristic impedance. The analysis of lossless lines provides an approximation for real transmission lines that simplifies the mathematics considered in modeling transmission lines. A lossless line is defined as a line that has no line resistance. This would imply that the conductors act like a perfect conductors, for a lossless line terminated in Z0, there is no loss of current across the line, and so the voltage remains the same along the line. The lossless line model is an approximation for many practical cases, such as low-loss transmission lines. For both of these cases, R and G are much smaller than ωL and ωC, respectively, without a reflection of the wave, the load that is being supplied by the line effectively blends into the line making it appear to be an infinite line. In a lossless line this implies that the voltage and current remain the same everywhere along the transmission line and their magnitudes remain constant along the length of the line and are only rotated by a phase angle. Loaded below its SIL, a line supplies reactive power to the system, above it, the line absorbs reactive power, tending to depress the voltage. The Ferranti effect describes the voltage gain towards the end of a very lightly loaded transmission line. Underground cables normally have a very low impedance, resulting in an SIL that is typically in excess of the thermal limit of the cable. Hence a cable is almost always a source of reactive power, ampères circuital law Characteristic acoustic impedance Electrical impedance Maxwells equations Transmission line Wave impedance Space cloth Guile, A. E. This article incorporates public domain material from the General Services Administration document Federal Standard 1037C
8.
Bayonet mount
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To couple the two parts, the pin on the male are aligned with the slot on the female and the two pushed together. Once the pins reach the bottom of the slot, one or both parts are rotated so that the pin slides along the arm of the L until it reaches the serif. The spring then pushes the male connector up into the serif to keep the pin locked into place, a practised user can connect them quickly and, unlike screw connectors, they are not subject to cross-threading. To disconnect, the two parts are pushed together to move the pin out of the serif while twisting in the opposite direction than for connecting, the strength of the joint comes from the strength of the pins and the L slots, and the spring. It is possible to push down the connector and rotate it, but not far enough to engage and lock, it will stay in place temporarily, Bayonet electrical connectors are used in the same applications where other connectors are used, to transmit either power or signals. Bayonet connections can be faster than screw connections, and more securely than push-fit connections. They may be used to two cables, or to connect a cable to a connector on the panel of a piece of equipment. The coupling system is made of two bayonet ramps machined on the external side of the receptacle connector and 2 stainless steel studs mounted inside the plug connector’s coupling nut. Several classes of electrical connectors, including audio, video. Examples include BNC, C, and ST connectors, the first documented use of this type of fitting may be by Al-Jazari in the 13th century, who used it to mount candles into his candle-clocks. This type of fitting was later used for soldiers who needed to mount bayonets to the ends of their rifles. The standard size is B22d-2, often referred to in the context of lighting as simply BC, older installations in some other countries, including France and Greece use this base. Examples of three-pin bulbs are found in street lamps and fireglow bulbs in some older models of electric radiative heater. Older railway carriages in the UK also made use of a 3 pin bulb base to discourage theft, Bayonet cap bulbs are also very common worldwide in applications where vibration may loosen screw-mount bulbs, such as automotive lighting and other small indicators, and in many flashlights. In many other countries the Edison screw base is used for lighting, newer bulbs use a wedge base which can be inserted either way with no issues. Some special-purpose bulbs, such as infra-red, have 3 pins 120 degrees apart to prevent them being used in any, Bayonet bases or caps are often abbreviated to BA, often with a number after. The number refers to the diameter of the base, bA15, a 15 mm base, can also be referred to as SBC standing for small bayonet cap. The lower-case letter s or d specifies whether the bulb has single or double contacts, while G actually indicates bi-pin, those listed above have a twist-lock, but with parallel pins from the end instead of opposing pins on the side
9.
TNC connector
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The TNC connector is a threaded version of the BNC connector. The connector has a 50 Ω impedance and operates best in the 0–11 GHz frequency spectrum and it has better performance than the BNC connector at microwave frequencies. Invented in the late 1950s and named after Paul Neill of Bell Labs and Carl Concelman of Amphenol, the abbreviation TNC is sometimes given as standing for Threaded Navy Connector. Reverse-polarity TNC is a variation of the TNC specification which reverses the polarity of the interface and this is usually achieved by incorporating the female contacts normally found in jacks into the plug, and the male contacts normally found in plugs into the jack. The FCC considered that the RP-TNC was acceptable in preventing consumers changing the antenna, as of 2013, leading manufacturers are still using RP-TNC connectors on their Wi-Fi equipment. Most TNC connectors are 50-ohm type even when used with coaxial cable of other impedances and these can be recognized by a reduced amount of dielectric in the mating ends. They are intermatable with standard types, RF connector SMA connector, SMB connector, SMC connector BNC connector, N connector Optical fiber connector
10.
Video
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Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video systems vary greatly in the resolution of the display and refresh rate, video can be carried on a variety of media, including radio broadcast, tapes, DVDs, computer files etc. Video was originally exclusively a live technology, charles Ginsburg led an Ampex research team developing one of the first practical video tape recorder. In 1951 the first video tape recorder captured live images from television cameras by converting the electrical impulses. Video recorders were sold for $50,000 in 1956, however, prices gradually dropped over the years, in 1971, Sony began selling videocassette recorder decks and tapes into the consumer market. The use of techniques in video created digital video, which allowed higher quality and, eventually. After the invention of the DVD in 1997 and Blu-ray Disc in 2006, sales of videotape, the advent of digital broadcasting and the subsequent digital television transition is in the process of relegating analog video to the status of a legacy technology in most parts of the world. PAL standards and SECAM specify 25 frame/s, while NTSC standards specify 29.97 frames, film is shot at the slower frame rate of 24 frames per second, which slightly complicates the process of transferring a cinematic motion picture to video. The minimum frame rate to achieve a comfortable illusion of an image is about sixteen frames per second. Video can be interlaced or progressive, analog display devices reproduce each frame in the same way, effectively doubling the frame rate as far as perceptible overall flicker is concerned. NTSC, PAL and SECAM are interlaced formats, abbreviated video resolution specifications often include an i to indicate interlacing. For example, PAL video format is specified as 576i50, where 576 indicates the total number of horizontal scan lines, i indicates interlacing. In progressive scan systems, each refresh period updates all scan lines in each frame in sequence, when displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary and moving parts of the image. Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material, aspect ratio describes the dimensions of video screens and video picture elements. All popular video formats are rectilinear, and so can be described by a ratio between width and height, the screen aspect ratio of a traditional television screen is 4,3, or about 1.33,1. High definition televisions use a ratio of 16,9. The aspect ratio of a full 35 mm film frame with soundtrack is 1.375,1. Therefore, a 720 by 480 pixel NTSC DV image displayes with the 4,3 aspect ratio if the pixels are thin, the popularity of viewing video on mobile phones has led to the growth of vertical video
11.
Serial digital interface
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Serial digital interface is a family of digital video interfaces first standardized by SMPTE in 1989. For example, ITU-R BT.656 and SMPTE 259M define digital video interfaces used for broadcast-grade video, a related standard, known as high-definition serial digital interface, is standardized in SMPTE 292M, this provides a nominal data rate of 1.485 Gbit/s. Additional SDI standards have been introduced to support increasing video resolutions, frame rates, stereoscopic video, 3G-SDI consists of a single 2.970 Gbit/s serial link that allows replacing dual link HD-SDI. 6G-SDI and 12G-SDI standards were published on March 19,2015 and these standards are used for transmission of uncompressed, unencrypted digital video signals within television facilities, they can also be used for packetized data. Coaxial variants of the range in length but are typically less than 300 meters. Fiber optic variants of the such as 297M allow for long-distance transmission limited only by maximum fiber length or repeaters. Several professional video and HD-video capable DSLR cameras and all uncompressed video capable consumer cameras use the HDMI interface, there are various mod kits for existing DVD players and other devices, which allow a user to add a serial digital interface to these devices. The various serial digital interface standards all use coaxial cables with BNC connectors and this is the same type of cable used in analog video setups, which potentially makes for easier upgrades. The specified signal amplitude at the source is 800 mV peak-to-peak, using equalization at the receiver, it is possible to send 270 Mbit/s SDI over 300 meters without use of repeaters, but shorter lengths are preferred. The HD bitrates have a maximum run length, typically 100 meters. Uncompressed digital component signals are transmitted, data is encoded in NRZI format, and a linear feedback shift register is used to scramble the data to reduce the likelihood that long strings of zeroes or ones will be present on the interface. The interface is self-synchronizing and self-clocking, * Working group 32NF-70 is in the process of developing standard ST-2083 for 24Gbit/s SDI. 270 Mbit/s is by far the most commonly used, though the 360 Mbit/s interface is sometimes encountered, the 143 and 177 Mbit/s interfaces were intended for transmission of composite-encoded video digitally, and are now considered obsolete. For enhanced definition applications, there are several 540 Mbit/s interfaces defined, for HDTV applications, the serial digital interface is defined by SMPTE 292M. Two bit rates are defined,1.485 Gbit/s, and 1. 485/1.001 Gbit/s. The factor of 1/1.001 is provided to allow SMPTE 292M to support video formats with rates of 59.94 Hz,29.97 Hz. The 1.485 Gbit/s version of the standard supports other frame rates in widespread use, including 60 Hz,50 Hz,30 Hz,25 Hz and it is common to collectively refer to both standards as using a nominal bit rate of 1.5 Gbit/s. For very high-definition applications, requiring resolution, frame rate, or color fidelity than the HD-SDI interface can provide
12.
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
13.
Avionics
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Avionics are the electronic systems used on aircraft, artificial satellites, and spacecraft. Avionic systems include communications, navigation, the display and management of systems. These can be as simple as a searchlight for a helicopter or as complicated as the tactical system for an airborne early warning platform. The term avionics is a portmanteau of the aviation and electronics. The term avionics was coined by the journalist Philip J. Klass as a portmanteau of aviation electronics, many modern avionics have their origins in World War II wartime developments. For example, autopilot systems that are today were started to help bomber planes fly steadily enough to hit precision targets from high altitudes. Famously, radar was developed in the UK, Germany, modern avionics is a substantial portion of military aircraft spending. Aircraft like the F‑15E and the now retired F‑14 have roughly 20 percent of their budget spent on avionics, most modern helicopters now have budget splits of 60/40 in favour of avionics. The civilian market has seen a growth in cost of avionics. Flight control systems and new navigation needs brought on by tighter airspaces, have pushed up development costs, the major change has been the recent boom in consumer flying. As more people begin to use planes as their method of transportation. The majority of power their avionics using 14- or 28‑volt DC electrical systems, however, larger. One source of international standards for equipment are prepared by the Airlines Electronic Engineering Committee. Communications connect the deck to the ground and the flight deck to the passengers. On‑board communications are provided by systems and aircraft intercoms. The VHF aviation communication system works on the airband of 118.000 MHz to 136.975 MHz, each channel is spaced from the adjacent ones by 8.33 kHz in Europe,25 kHz elsewhere. VHF is also used for line of communication such as aircraft-to-aircraft. Amplitude modulation is used, and the conversation is performed in simplex mode, aircraft communication can also take place using HF or satellite communication
14.
Electronic test equipment
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Electronic test equipment is used to create signals and capture responses from electronic devices under test. In this way, the operation of the DUT can be proven or faults in the device can be traced. Use of electronic test equipment is essential to any work on electronics systems. ATE often includes many of instruments in real and simulated forms. Generally, more advanced test gear is necessary when developing circuits, designing a test system’s switching configuration requires an understanding of the signals to be switched and the tests to be performed, as well as the switching hardware form factors available. The following items are used for measurement of voltages, currents. Voltmeter Ohmmeter Ammeter, e. g. Galvanometer or Milliameter Multimeter e. g. VOM or DMM RLC Meter e. g and these systems are widely employed for incoming inspection, quality assurance, and production testing of electronic devices and subassemblies. The General Purpose Interface Bus is an IEEE-488 standard parallel interface used for attaching sensors, GPIB is a digital 8-bit parallel communications interface capable of achieving data transfers of more than 8 Mbytes/s. It allows daisy-chaining up to 14 instruments to a system using a 24-pin connector. It is one of the most common I/O interfaces present in instruments and is designed specifically for instrument control applications, the IEEE-488 specifications standardized this bus and defined its electrical, mechanical, and functional specifications, while also defining its basic software communication rules. GPIB works best for applications in industrial settings that require a connection for instrument control. The original GPIB standard was developed in the late 1960s by Hewlett-Packard to connect, the introduction of digital controllers and programmable test equipment created a need for a standard, high-speed interface for communication between instruments and controllers from various vendors. This standard was revised in 1978 and 1990. The IEEE488.2 specification includes the Standard Commands for Programmable Instrumentation, SCPI ensures compatibility and configurability among these instruments. The IEEE-488 bus has long been popular because it is simple to use and takes advantage of a selection of programmable instruments. Large systems, however, have the limitations, Driver fanout capacity limits the system to 14 devices plus a controller. Cable length limits the distance to two meters per device or 20 meters total, whichever is less. This imposes transmission problems on systems spread out in a room or on systems that require remote measurements, primary addresses limit the system to 30 devices with primary addresses
15.
Electrical termination
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Electrical termination is an electrical industry term used to describe the specific point at which a conductive device, such as wire or cable, ends or starts. The conductive device may or may not pass the carried electricity or signal onto another conductive device at this point, a common point of electrical termination is at a terminal block. A wire typically ends, or terminates, at the terminal block, ordinary electrical cables suffice to carry low frequency alternating current, such as mains power, which reverses direction 100 to 120 times per second, and audio signals. However, they cannot be used to carry currents in the frequency range, above about 30 kHz, because the energy tends to radiate off the cable as radio waves. The higher the frequency of waves moving through a given cable or medium. Transmission lines become necessary when the length of the cable is longer than a significant fraction of the transmitted frequencys wavelength, types of transmission line cables include parallel line, and coaxial cable. and these require high frequency signal termination. The terminator is usually placed at the end of a line or daisy chain bus, and is designed to match the AC impedance of the cable and hence minimize signal reflections. Less commonly, a terminator is also placed at the end of the wire or cable. Radio frequency currents tend to reflect from discontinuities in the such as connectors and joints. Secondary reflections can also occur at the start, allowing interference to persist as repeated echoes of old data. These reflections also act as bottlenecks, preventing the signal power from reaching the destination, transmission line cables require impedance matching to carry electromagnetic signals with minimal reflections and power losses. Signal terminators are designed to match the characteristic impedances at both cable ends. Types of transmission line cables include balanced line such as line, and twisted pairs. Passive terminators often consist of a resistor, however significantly reactive loads may require other passive components such as inductors, capacitors. Active terminators consist of a regulator that keeps the voltage used for the terminating resistor at a constant level. Forced Perfect Termination Forced Perfect Termination can be used on single ended buses where diodes remove over, the signal is locked between two actively regulated voltage levels, which results in superior performance over a standard active terminator. All parallel SCSI units use terminators, SCSI is primarily used for storage and backup. Controller area network, commonly known as CAN Bus, uses terminators consisting of a 120 ohm resistor, dummy loads are commonly used in HF to EHF frequency circuits
16.
Composite video
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Composite video is an analog video transmission that carries standard definition video typically at 480i or 576i resolution. Video information is encoded on one channel, unlike the higher-quality S-video, Composite video is usually in standard formats such as NTSC, PAL, and SECAM and is often designated by the CVBS initialism, for color, video, blanking and sync, or simply as video. A composite video signal combines on one wire the video information required to recreate a picture, as well as line. The color video signal is a combination of the luminance of the picture, and a modulated subcarrier carries the chrominance or color information. Details of the process vary between the NTSC, PAL and SECAM systems. The burst signal is inverted in phase from the reference subcarrier, Composite video can easily be directed to any broadcast channel simply by modulating the proper RF carrier wave with it. On playback, these devices often give the user the option to output the signal or to modulate it onto a VHF or UHF frequency compatible with a TV tuner. In home applications, the video signal is typically connected using an RCA connector. It is often accompanied with red and white connectors for right, BNC connectors and higher quality coaxial cable are often used in professional television studios and post-production applications. BNC connectors were used for composite video connections on early home VCRs. The BNC connector, in turn post dated the PL-259 connector which featured on first generation VCRs. In Europe, SCART connections are used instead of RCA jacks, so where available, RGB is used instead of composite video with computers, video game consoles. Video cables are 75 ohm impedance, low in capacitance, typical values run from 52 pF/m for an HDPE-foamed dielectric precision video cable to 69 pF/m for a solid PE dielectric cable. Some devices that connect to a TV, such as VCRs, older video game consoles and home computers of the 1980s and this may then be converted to RF with an external box known as an RF modulator that generates the proper carrier. Sometimes this modulator was built into the product and sometimes it was a unit powered by the computer or with an independent power supply. In the United States, using an external RF modulator frees the manufacturer from obtaining FCC approval for each variation of a device, Video game consoles on the other hand were less of an issue with FCC approval because the circuitry was inexpensive enough to allow for channel 3/4 outputs. Modern day devices with analog outputs have typically omitted channel 3 and 4 outputs in favor of composite and S-video outputs as composite, in addition, many TV sets sold these days no longer have analog television tuners and cannot accept channel 3/4. The process of modulating RF with the video signal, and then demodulating the original signal again in the TV
17.
Consumer electronics
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Consumer electronics or home electronics are electronic or digital equipment intended for everyday use, typically in private homes. Consumer electronics include devices used for entertainment, communications, and home-office activities, in British English, they are often called brown goods by producers and sellers, to distinguish them from white goods such as washing machines and refrigerators. Radio broadcasting in the early 20th century brought the first major consumer product, later products included telephones, personal computers, MP3 players, audio equipment, televisions and calculators. In the 2010s, consumer electronics stores often sell GPS, automotive electronics, video game consoles, electronic instruments, karaoke machines, digital cameras. Stores also sell digital cameras, camcorders, cell phones, some consumer electronics stores, such as Best Buy have also begun selling office and baby furniture. Consumer electronics stores may be bricks and mortar retail stores, online stores. The CEA estimated the value of 2015 consumer electronics sales at US$220 billion, for its first fifty years the phonograph turntable did not use electronics, the needle and soundhorn were purely mechanical technologies. However, in the 1920s radio broadcasting became the basis of production of radio receivers. The vacuum tubes that had made radios practical were used with record players as well, television was soon invented, but remained insignificant in the consumer market until the 1950s. The transistor, invented in 1947 by Bell Laboratories, led to significant research in the field of semiconductors in the early 1950s. The transistors advantages revolutionized that industry along with other electronics, by 1959 Fairchild Semiconductor had introduced the first planar transistor from which come the origins of Moores Law. Integrated circuits followed when manufacturers built circuits on a substrate using electrical connections between circuits within the chip itself. One overriding characteristic of consumer products is the trend of ever-falling prices. This is driven by gains in manufacturing efficiency and automation, lower costs as manufacturing has moved to lower-wage countries. Semiconductor components benefit from Moores Law, a principle which states that, for a given price. While consumer electronics continues in its trend of convergence, combining elements of many products, there is an ever increasing need to keep product information updated and comparable, for the consumer to make an informed choice. Style, price, specification, and performance are all relevant, there is a gradual shift towards e-commerce web-storefronts. Many products include Internet connectivity using technologies such as Wi-Fi, Bluetooth, products not traditionally associated with computer use now provide options to connect to the Internet or to a computer using a home network to provide access to digital content
18.
RCA connector
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An RCA connector, sometimes called a phono connector or Cinch connector, is a type of electrical connector commonly used to carry audio and video signals. The connectors are sometimes casually referred to as A/V jacks. The name RCA derives from the Radio Corporation of America, which introduced the design by the early 1940s for internal connection of the pickup to the chassis in home radio-phonograph consoles. It was originally a low-cost, simple design, intended only for mating, refinement came with later designs, although they remained compatible. However, quarter-inch phone connectors are common in professional audio. The connections plug is called an RCA plug or phono plug, the name phono plug is sometimes confused with a phone plug which may refer to a quarter-inch phone plug – Tip/Sleeve or Tip/Ring/Sleeve connector – or to a 4P4C connector used for a telephone. In the most normal use, cables have a plug on each end, consisting of a central male connector. The ring is often segmented for flexibility, devices mount the socket, consisting of a central hole with a ring of metal around it. The ring is smaller in diameter and longer than the ring on the plug. The jack has an area between the outer and inner rings which is filled with an insulator, typically plastic. Its use as a connector for video signals is extremely common. RCA connectors and cable are commonly used to carry S/PDIF-formatted digital audio. Connections are made by pushing the cables plug into the jack on the device. Continuous noise can occur if the plug partially falls out of the jack, breaking ground connection, some variants of the plug, especially cheaper versions, also give very poor grip and contact between the ground sheaths due to their lack of flexibility. They are often color-coded, yellow for composite video, red for the audio channel. This trio of jacks can be found on the back of almost all audio, one or more sets are often found on TV sets to facilitate connection of camcorders, other portable video sources and video game consoles. Varying cable quality means that a cheap line-level audio cable might not successfully transfer component video, cables should meet the S/PDIF specification as defined by the international standard IEC 60958-3 for assured performance. The male plug has a pin which is 3.175 mm in diameter
19.
Network interface controller
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A network interface controller is a computer hardware component that connects a computer to a computer network. Early network interface controllers were commonly implemented on expansion cards that plugged into a computer bus, the low cost and ubiquity of the Ethernet standard means that most newer computers have a network interface built into the motherboard. The network controller implements the electronic circuitry required to communicate using a physical layer and data link layer standard such as Ethernet, Fibre Channel. The NIC allows computers to communicate over a network, either by using cables or wirelessly. Although other network technologies exist, IEEE802 networks including the Ethernet variants have achieved near-ubiquity since the mid-1990s, newer server motherboards may even have dual network interfaces built-in. The Ethernet capabilities are integrated into the motherboard chipset or implemented via a low-cost dedicated Ethernet chip. A separate network card is not required unless additional interfaces are needed or some type of network is used. The NIC may use one or more of the techniques to indicate the availability of packets to transfer. Interrupt-driven I/O is where the peripheral alerts the CPU that it is ready to transfer data, also, NICs may use one or more of the following techniques to transfer packet data, Programmed input/output is where the CPU moves the data to or from the NIC to memory. Direct memory access is where some other device other than the CPU assumes control of the bus to move data to or from the NIC to memory. This removes load from the CPU but requires more logic on the card, in addition, a packet buffer on the NIC may not be required and latency can be reduced. There are two types of DMA, third-party DMA in which a DMA controller other than the NIC performs transfers, an Ethernet network controller typically has an 8P8C socket where the network cable is connected. Older NICs also supplied BNC, or AUI connections, a few LEDs inform the user of whether the network is active, and whether or not data transmission occurs. Ethernet network controllers typically support 10 Mbit/s Ethernet,100 Mbit/s Ethernet, such controllers are designated as 10/100/1000, meaning that they can support a notional maximum transfer rate of 10,100 or 1000 Mbit/s. 10 Gigabit Ethernet NICs are also available, and, as of November 2014, are beginning to be available on computer motherboards, multiqueue NICs provide multiple transmit and receive queues, allowing packets received by the NIC to be assigned to one of its receive queues. The hardware-based distribution of the interrupts, described above, is referred to as receive-side scaling, purely software implementations also exist, such as the receive packet steering and receive flow steering. Examples of such implementations are the RFS and Intel Flow Director, with multiqueue NICs, additional performance improvements can be achieved by distributing outgoing traffic among different transmit queues. By assigning different transmit queues to different CPUs/cores, various operating systems internal contentions can be avoided and those NICs support, Accessing local and remote memory without involving the remote CPU
20.
Wire stripper
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A wire stripper is a small, hand-held device used to strip the electrical insulation from electric wires. A simple manual wire stripper is a pair of opposing blades much like scissors or wire cutters, the addition of a center notch makes it easier to cut the insulation without cutting the wire. This type of wire stripper is used by rotating it around the insulation while applying pressure in order to make a cut around the insulation, since the insulation is not bonded to the wire, it then pulls easily off the end. This is the most versatile type of wire stripper, another type of manual wire stripper is very similar to the simple design previously mentioned, except this type has several notches of varying size. This allows the user to match the size to the wire size. Once the device is clamped on, the remainder of the wire can simply be pulled out, the automatic wire stripper was first patented in 1915 by Stuart G. Wood of Brooklyn, NY. The design was refined by Herman Gerhard Jan Voogd of the Netherlands eliminating the awkward 4 bar mechanism taking on the outline that It has kept since. A second actuation released the mechanism to return to the rest position, the action was further refined by Wood and finally by Eugene D. Hindenburg of DeKalb, IL. When engaged, an automatic wire stripper first simultaneously grips the wire in one side, after the sides have completed their stroke the two sides of the mechanism spread apart to push the cut tube of insulation from the end of the conductor. To use it, one simply has to place the wire in the jaws in the slot the size of the conductor. This device allows even a novice to strip most wires very quickly, the automatic wire strippers cutter must be short, because it causes the jaws to twist, as described by Wood in the 1943 patent. All wire strippers are inherently limited to those wire sizes the cutting jaw notches will accommodate, an automatic wire strippers short cutter limits it to fewer notches and a smaller range of wire sizes than most other types of wire strippers. The accuracy of the cutting blade opening determines the smallest conductor that can be reliably stripped, if the cutter opening is to small it will impinge on the conductor causing excess friction and more tension than the wire can withstand. If the cutter opening is too large the tension required to tear the remaining annulus of uncut insulation may be greater than the wire can withstand, some models have an adjustable grip tension, to adjust the clamping force of the gripping jaw. The knob below the jaw on the yellow automatic strippers in the image below is a grip tension adjustment, a laser wire stripper is a computer-controlled machine, much like a CNC router, which uses a laser to burn off the insulation of the wire. Laser wire stripping machines are used mostly for very fine gauge wires since they do not damage the conductor, a typical CO2 laser wire stripping machine should be capable of stripping the insulation from any size wire. Electrical hand tools Linemans pliers Needle-nose pliers
21.
Bell Labs
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Nokia Bell Labs is an American research and scientific development company, owned by Finnish company Nokia. Its headquarters are located in Murray Hill, New Jersey, in addition to laboratories around the rest of the United States. The historic laboratory originated in the late 19th century as the Volta Laboratory, Bell Labs was also at one time a division of the American Telephone & Telegraph Company, half-owned through its Western Electric manufacturing subsidiary. Eight Nobel Prizes have been awarded for work completed at Bell Laboratories, in 1880, the French government awarded Alexander Graham Bell the Volta Prize of 50,000 francs, approximately US$10,000 at that time for the invention of the telephone. Bell used the award to fund the Volta Laboratory in Washington, D. C. in collaboration with Sumner Tainter, the laboratory is also variously known as the Volta Bureau, the Bell Carriage House, the Bell Laboratory and the Volta Laboratory. The laboratory focused on the analysis, recording, and transmission of sound, Bell used his considerable profits from the laboratory for further research and education to permit the diffusion of knowledge relating to the deaf. This resulted in the founding of the Volta Bureau c,1887, located at Bells fathers house at 1527 35th Street in Washington, D. C. where its carriage house became their headquarters in 1889. In 1893, Bell constructed a new building, close by at 1537 35th St. specifically to house the lab, the building was declared a National Historic Landmark in 1972. In 1884, the American Bell Telephone Company created the Mechanical Department from the Electrical, the first president of research was Frank B. Jewett, who stayed there until 1940, ownership of Bell Laboratories was evenly split between AT&T and the Western Electric Company. Its principal work was to plan, design, and support the equipment that Western Electric built for Bell System operating companies and this included everything from telephones, telephone exchange switches, and transmission equipment. Bell Labs also carried out consulting work for the Bell Telephone Company, a few workers were assigned to basic research, and this attracted much attention, especially since they produced several Nobel Prize winners. Until the 1940s, the principal locations were in and around the Bell Labs Building in New York City. Of these, Murray Hill and Crawford Hill remain in existence, the largest grouping of people in the company was in Illinois, at Naperville-Lisle, in the Chicago area, which had the largest concentration of employees prior to 2001. Since 2001, many of the locations have been scaled down or closed. The Holmdel site, a 1.9 million square foot structure set on 473 acres, was closed in 2007, the mirrored-glass building was designed by Eero Saarinen. In August 2013, Somerset Development bought the building, intending to redevelop it into a commercial and residential project. The prospects of success are clouded by the difficulty of readapting Saarinens design and by the current glut of aging, eight Nobel Prizes have been awarded for work completed at Bell Laboratories
22.
N connector
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The N connector is a threaded, weatherproof, medium-size RF connector used to join coaxial cables. It was one of the first connectors capable of carrying microwave-frequency signals, originally, the connector was designed to carry signals at frequencies up to 1 GHz in military applications, but todays common Type N easily handles frequencies up to 11 GHz. More recent precision enhancements to the design by Julius Botka at Hewlett Packard have pushed this to 18 GHz, the male connector is hand-tightened and has an air gap between the center and outer conductors. The coupling has a 5/8-24 thread, the center coaxial contacts are identical to TNC and BNC connectors. Amphenol suggests tightening to a torque of 15 inch-pounds, while Andrew Corporation suggest 20 inch-pounds for their hex nut variant, the peak power rating of an N connector is determined by voltage breakdown/ionisation of the air near the center pin. The average power rating is determined by overheating of the contact due to resistive insertion loss. Typical makers curves for a new clean connector with a perfect load give limits of ≈5000 W at 20 MHz and this square root frequency derating law is expected from the skin depth decreasing with frequency. At lower frequencies the same maker recommends an upper bound of ≈1000 V RMS, the N connector follows the MIL-STD-348 standard, defined by the US military, and comes in 50 and 75 ohm versions. The 50 ohm version is used in the infrastructure of land mobile, wireless data, paging. The 75 ohm version is used in the infrastructure of cable television systems. Connecting these two different types of connectors to each other can lead to damage, and/or intermittent operation due to the difference in diameter of the center pin. Unfortunately, many type N connectors are not labeled, and it can be difficult to prevent this situation in a mixed impedance environment. The 50 ohm type N connector is favored by enthusiasts who create their own Wireless LAN antenna systems, the Cantenna is one such design. The enthusiasts have settled on using the N connector as a connection for homebrew antennas. By using a cable with an N connector one can easily interchange homebrew antennas,50 Ω N connectors are also commonly used on amateur radio devices operating in UHF bands. A male N-connector can plug into an female SnapN, the HN connector is slightly larger and is designed for high-voltage applications. RF connector SMA connector, SMB connector, SMC connector UHF connector Optical fiber connector ^ N type connectors from Cmpter Electronics
23.
Amphenol
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Amphenol Corporation is a major producer of electronic and fiber optic connectors, cable and interconnect systems such as coaxial cables. Amphenol is a portmanteau from the original name, American Phenolic Corp. Amphenol was founded in Chicago in 1932 by entrepreneur Arthur J. Schmitt, Amphenol expanded significantly during World War II, when the company became the primary manufacturer of connectors used in military hardware, including airplanes and radios. From 1967 to 1982 it was part of Bunker Ramo Corporation, Amphenols revenues in 2010 were $3.55 billion. Operations are located in more than 60 locations around the world, the company is included in the S&P Midcap 400 index. Amphenols Chairman is Dr. Martin H. Loeffler, Amphenols world headquarters is located in Wallingford, Connecticut. The largest division of Amphenol is Amphenol Aerospace in Sidney, New York and this is the birthplace of the MIL-DTL-38999 cylindrical connector. Amphenol engineers also invented the commonly used BNC connector, Amphenol Fiber Systems International is a fiber optic company started in 1993 that specializes in the fabrication and manufacturing of fiber optic connectivity products and systems. AFSI provides solutions for systems based on fiber optic interconnect technology. AFSI employs over 100 people at its 50,000 square foot facility in the heart of the corridor in Allen. Amphenol Cables on Demand, another division of Amphenol launched in December 2006 and they sell more than 2500 audio, video, computer, and networking cables. Offices are located in New York, California, Florida, Toronto, in May 2005, Amphenol acquired SV Microwave, a manufacturer of RF connectors, components and cable assemblies. On October 10,2005, Teradyne and Amphenol announced that Amphenol would acquire Teradyne Connection Systems, TCS, based in Nashua, New Hampshire, manufactures high-density electronic connectors, complete backplanes, and systems packaging, a product line that complements Amphenols existing lines of business. In February 2008, Amphenol acquired SEFEE, a French electronic manufacturer, Jaybeam Wireless became Amphenol Jaybeam and is now Amphenol Antenna Solutions. On November 15,2013, Amphenol announced it had entered an agreement to acquire Advanced Sensors Business of GE for approx. On January 8,2016, Amphenol finalized its deal to acquire FCI Asia Pte Ltd an interconnect company specializing in the telecom, datacom, in July 2016, Amphenol acquired AUXELFTG, a French manufacturer of power busbars and power interconnect solutions. Notes Official website Amphenol SEC Filings Amphenol LTW - Innovation in Waterproof Solution Amphenol Aerospace Amphenol Cables on Demand Amphenol RF
24.
C connector
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The C connector is a type of RF connector used for terminating coaxial cable. The C connector was invented by Amphenol engineer Carl Concelman and it is weatherproof without being overly bulky. The mating arrangement is similar to that of the BNC connector
25.
Backronym
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A backronym or bacronym is a specially constructed phrase that is supposed to be the source of a word that is, or is claimed to be, an acronym. Backronyms may be invented with serious or humorous intent, or may be a type of false or folk etymology, the word is a combination of backward and acronym, and has been defined as a reverse acronym. Its earliest known citation in print is as bacronym in the November 1983 edition of the Washington Post monthly neologism contest. The newspaper quoted winning reader Meredith G. Williams of Potomac, Maryland, defining it as the same as an acronym, except that the words were chosen to fit the letters. An acronym is a derived from the initial letters of the words of a phrase, For example. By contrast, a backronym is constructed by creating a new phrase to fit an existing word, name. Backronyms are also used for comedic effect, as exemplified by NASAs C. O. L. B. E. R. T. NASA named its ISS treadmill the Combined Operational Load-Bearing External Resistance Treadmill after Stephen Colbert, the backronym was a lighthearted compromise in recognition of the comedians ability to sway NASAs online vote for the naming of an ISS module. Backronyms can be constructed for educational purposes, for example to form mnemonics, an example of such a mnemonic is the Apgar score, used to assess the health of newborn babies. Alcoholics Anonymous and other 12-step programs use backronyms as teaching tools, similar to such as one day at a time, or Let go, let God. For example, a slip may be expanded as Sobriety Losing Its Priority, backronyms are also created as jokes or as slogans, often expressing consumer loyalties or frustration. For example, the name of the restaurant chain Arbys is a play on the letters RB, referring to the companys founders, an advertising campaign in the 1980s created a backronym with the slogan America’s Roast Beef, Yes Sir. Many companies or products have spawned multiple humorous backronyms, with positive connotations asserted by supporters or negative ones by detractors. For example, the car company Ford was said to stand for First On Race Day, by aficionados, similar backronyms have been directed against many other automakers, such as Fix It Again Tony for Fiat. Backronyms have also coined by military personnel during wartime. The backronym for Spam, Something Posing As Meat, was said to have originated from jaundiced soldiers who were sick of eating canned meat. The British contribution to the 2003 invasion of Iraq was code-named Operation Telic, backronyms are sometimes created to name laws or programs. Commentators have noted a trend among US lawmakers to devise names that form a desired acronym
26.
Ohm
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The ohm is the SI derived unit of electrical resistance, named after German physicist Georg Simon Ohm. The definition of the ohm was revised several times, today the definition of the ohm is expressed from the quantum Hall effect. In many cases the resistance of a conductor in ohms is approximately constant within a range of voltages, temperatures. In alternating current circuits, electrical impedance is also measured in ohms, the siemens is the SI derived unit of electric conductance and admittance, also known as the mho, it is the reciprocal of resistance in ohms. The power dissipated by a resistor may be calculated from its resistance, non-linear resistors have a value that may vary depending on the applied voltage. The rapid rise of electrotechnology in the last half of the 19th century created a demand for a rational, coherent, consistent, telegraphers and other early users of electricity in the 19th century needed a practical standard unit of measurement for resistance. Two different methods of establishing a system of units can be chosen. Various artifacts, such as a length of wire or a standard cell, could be specified as producing defined quantities for resistance, voltage. This latter method ensures coherence with the units of energy, defining a unit for resistance that is coherent with units of energy and time in effect also requires defining units for potential and current. Some early definitions of a unit of resistance, for example, the absolute-units system related magnetic and electrostatic quantities to metric base units of mass, time, and length. These units had the advantage of simplifying the equations used in the solution of electromagnetic problems. However, the CGS units turned out to have impractical sizes for practical measurements, various artifact standards were proposed as the definition of the unit of resistance. In 1860 Werner Siemens published a suggestion for a reproducible resistance standard in Poggendorffs Annalen der Physik und Chemie and he proposed a column of pure mercury, of one square millimetre cross section, one metre long, Siemens mercury unit. However, this unit was not coherent with other units, one proposal was to devise a unit based on a mercury column that would be coherent – in effect, adjusting the length to make the resistance one ohm. Not all users of units had the resources to carry out experiments to the required precision. The BAAS in 1861 appointed a committee including Maxwell and Thomson to report upon Standards of Electrical Resistance, in the third report of the committee,1864, the resistance unit is referred to as B. A. unit, or Ohmad. By 1867 the unit is referred to as simply Ohm, the B. A. ohm was intended to be 109 CGS units but owing to an error in calculations the definition was 1. 3% too small. The error was significant for preparation of working standards, on September 21,1881 the Congrès internationale délectriciens defined a practical unit of Ohm for the resistance, based on CGS units, using a mercury column at zero deg
27.
Dielectric
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A dielectric material is an electrical insulator that can be polarized by an applied electric field. Because of dielectric polarization, positive charges are displaced toward the field and this creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, the study of dielectric properties concerns storage and dissipation of electric and magnetic energy in materials. Dielectrics are important for explaining various phenomena in electronics, optics, solid-state physics, while the term insulator implies low electrical conduction, dielectric typically means materials with a high polarizability. The latter is expressed by a called the relative permittivity. The term insulator is generally used to indicate electrical obstruction while the term dielectric is used to indicate the energy storing capacity of the material, a common example of a dielectric is the electrically insulating material between the metallic plates of a capacitor. The polarization of the dielectric by the electric field increases the capacitors surface charge for the given electric field strength. The term dielectric was coined by William Whewell in response to a request from Michael Faraday, a perfect dielectric is a material with zero electrical conductivity, thus exhibiting only a displacement current, therefore it stores and returns electrical energy as if it were an ideal capacitor. The electric susceptibility χe of a material is a measure of how easily it polarizes in response to an electric field. This, in turn, determines the electric permittivity of the material and thus many other phenomena in that medium. The susceptibility of a medium is related to its relative permittivity εr by χ e = ε r −1, so in the case of a vacuum, χ e =0. The electric displacement D is related to the polarization density P by D = ε0 E + P = ε0 E = ε r ε0 E, in general, a material cannot polarize instantaneously in response to an applied field. The more general formulation as a function of time is P = ε0 ∫ − ∞ t χ e E d t ′ and that is, the polarization is a convolution of the electric field at previous times with time-dependent susceptibility given by χe. The upper limit of this integral can be extended to infinity as well if one defines χe =0 for Δt <0, an instantaneous response corresponds to Dirac delta function susceptibility χe = χeδ. It is more convenient in a system to take the Fourier transform. Due to the theorem, the integral becomes a simple product. Note the simple frequency dependence of the susceptibility, or equivalently the permittivity, the shape of the susceptibility with respect to frequency characterizes the dispersion properties of the material. In the classical approach to the model, a material is made up of atoms
28.
Glass cockpit
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A glass cockpit is an aircraft cockpit that features electronic flight instrument displays, typically large LCD screens, rather than the traditional style of analog dials and gauges. This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information and they are also popular with airline companies as they usually eliminate the need for a flight engineer, saving costs. In recent years the technology has become available in small aircraft. As aircraft displays have modernized, the sensors that feed them have modernized as well, traditional gyroscopic flight instruments have been replaced by electronic attitude and heading reference systems and air data computers, improving reliability and reducing cost and maintenance. GPS receivers are usually integrated into glass cockpits, glass cockpits originated in military aircraft in the late 1960s and early 1970s, an early example is the Mark II avionics of the F-111D, which featured a multi-function display. Prior to the 1970s, air operations were not considered sufficiently demanding to require advanced equipment like electronic flight displays. Also, computer technology was not at a level where sufficiently light, the increasing complexity of transport aircraft, the advent of digital systems and the growing air traffic congestion around airports began to change that. The success of the NASA-led glass cockpit work is reflected in the acceptance of electronic flight displays beginning with the introduction of the MD-80 in 1979. Airlines and their passengers alike have benefited, the safety and efficiency of flights have been increased with improved pilot understanding of the aircrafts situation relative to its environment. By the end of the 1990s, liquid-crystal display panels were increasingly favored among aircraft manufacturers because of their efficiency, earlier LCD panels suffered from poor legibility at some viewing angles and poor response times, making them unsuitable for aviation. The glass cockpit has become standard equipment in airliners, business jets and it was fitted into NASAs Space Shuttle orbiters Atlantis, Columbia, Discovery, and Endeavour, and the current Russian Soyuz TMA model spacecraft that was launched in 2002. By the end of the century glass cockpits began appearing in general aviation aircraft as well, in 2003, Cirrus Designs SR20 and SR22 became the first light aircraft equipped with glass cockpits, which they made standard on all Cirrus aircraft. The Lockheed Martin F-35 Lightning II features a panoramic cockpit display touchscreen that replaces most of the switches and toggles found in an aircraft cockpit and they look and behave very similarly to other computers, with windows and data that can be manipulated with point-and-click devices. They also add terrain, approach charts, weather, vertical displays, the improved concepts enable aircraft makers to customize cockpits to a greater degree than previously. All of the manufacturers involved have chosen to do so in one way or another—such as using a trackball, many of the modifications offered by the aircraft manufacturers improve situational awareness and customize the human-machine interface to increase safety. Modern glass cockpits might include Synthetic Vision or Enhanced Vision systems, Enhanced Vision systems add real-time information from external sensors, such as an infrared camera. All new airliners such as the Airbus A380, Boeing 787 and private jets such as Bombardier Global Express, many modern general aviation aircraft are available with glass cockpits. Systems such as the Garmin G1000 are now available on many new GA aircraft, many small aircraft can also be modified post-production to replace analogue instruments
29.
Antenna (radio)
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In radio and electronics, an antenna, or aerial, is an electrical device which converts electric power into radio waves, and vice versa. It is usually used with a transmitter or radio receiver. In reception, an antenna intercepts some of the power of a wave in order to produce a tiny voltage at its terminals. Antennas are essential components of all equipment that uses radio, typically an antenna consists of an arrangement of metallic conductors, electrically connected to the receiver or transmitter. These time-varying fields radiate away from the antenna into space as a transverse electromagnetic field wave. Antennas can be designed to transmit and receive radio waves in all directions equally. The first antennas were built in 1888 by German physicist Heinrich Hertz in his experiments to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed dipole antennas at the point of parabolic reflectors for both transmitting and receiving. He published his work in Annalen der Physik und Chemie, the words antenna and aerial are used interchangeably. Occasionally the term aerial is used to mean a wire antenna, however, note the important international technical journal, the IEEE Transactions on Antennas and Propagation. In the United Kingdom and other areas where British English is used, the origin of the word antenna relative to wireless apparatus is attributed to Italian radio pioneer Guglielmo Marconi. In the summer of 1895, Marconi began testing his wireless system outdoors on his fathers estate near Bologna, Marconi discovered that by raising the aerial wire above the ground and connecting the other side of his transmitter to ground, the transmission range was increased. Soon he was able to transmit signals over a hill, a distance of approximately 2.4 kilometres, in Italian a tent pole is known as lantenna centrale, and the pole with the wire was simply called lantenna. Until then wireless radiating transmitting and receiving elements were simply as aerials or terminals. Because of his prominence, Marconis use of the word spread among wireless researchers. In common usage, the antenna may refer broadly to an entire assembly including support structure, enclosure. Especially at microwave frequencies, an antenna may include not only the actual electrical antenna. An antenna, in converting radio waves to electrical signals or vice versa, is a form of transducer, Antennas are required by any radio receiver or transmitter to couple its electrical connection to the electromagnetic field
30.
Patch panel
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Patch panels are commonly used in computer networking, recording studios, radio and television. Patchbays make it easier to connect different devices in different orders for different projects and this means that devices mounted in racks or keyboard instruments can be connected without having to hunt around behind the rack or instrument with a flashlight for the right jack. Using a patchbay also saves wear and tear on the jacks of studio gear and instruments. Patch panels are being used more prevalently in domestic installations, owing to the popularity of Structured Wiring installs and they are also found in home cinema installations more and more. It is conventional to have the top row of jacks wired at the rear to outputs, patch bays may be half-normal or full-normal, normal indicating that the top and bottom jacks are connected internally. With top half-normal wiring, the same happens but vice versa, if a patch bay is wired to full-normal, then it includes break contacts in both rows of jacks. Dedicated switching equipment can be an alternative to patch bays in some applications, switches can make routing as easy as pushing a button, and can provide other benefits over patch bays, including routing a signal to any number of destinations simultaneously. However, switching equipment that can emulate the capabilities of a patch bay is much more expensive. There are various types of switches for audio and video, from simple selector switches to sophisticated production switchers, however, emulating or exceeding the capabilities of audio and/or video patch bays requires specialized devices like routing switches and crossbar switches. Switching equipment may be electronic, mechanical, or electro-mechanical, some switcher hardware can be controlled via computer and/or other external devices. Some have automated and/or pre-programmed operational capabilities, there are also software switcher applications used to route signals and control data within a pure digital computer environment. Distribution frames are cheaper, but less convenient, cable management Wiring closet This article incorporates public domain material from the General Services Administration document Federal Standard 1037C
31.
Central apparatus room
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Some broadcast facilities have several of these rooms. It should be air-conditioned, however low-noise specifications such as acoustical treatments are optional, equipment is connected either directly with an attached foldout monitor, keyboard and mouse or remotely via KVM switch, ssh, VNC, or remote desktop. These rooms contain broadcast and broadcast IT mission critical gear necessary to broadcast and they contain broadcast and monitoring equipment, through which all the operations are monitored by the Transmission Engineer, without disturbing the Studio Recordings. Broadcast engineering Data center Master control room Network operations center Production control room Server room Server farm Transmission control room
32.
Stainless steel
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In metallurgy, stainless steel, also known as inox steel or inox from French inoxydable, is a steel alloy with a minimum of 10. 5% chromium content by mass. Stainless steel is notable for its resistance, and it is widely used for food handling. Stainless steel does not readily corrode, rust or stain with water as ordinary steel does, however, it is not fully stain-proof in low-oxygen, high-salinity, or poor air-circulation environments. There are various grades and surface finishes of stainless steel to suit the environment the alloy must endure, Stainless steel is used where both the properties of steel and corrosion resistance are required. Stainless steel differs from carbon steel by the amount of chromium present, unprotected carbon steel rusts readily when exposed to air and moisture. This iron oxide film is active and accelerates corrosion by making it easier for more iron oxide to form, since iron oxide has lower density than steel, the film expands and tends to flake and fall away. In comparison, stainless steels contain sufficient chromium to undergo passivation and this layer prevents further corrosion by blocking oxygen diffusion to the steel surface and stops corrosion from spreading into the bulk of the metal. Passivation occurs only if the proportion of chromium is high enough, Stainless steel’s resistance to corrosion and staining, low maintenance, and familiar lustre make it an ideal material for many applications. Storage tanks and tankers used to transport orange juice and other food are made of stainless steel. This also influences its use in kitchens and food processing plants, as it can be steam-cleaned and sterilized. High oxidation resistance in air at ambient temperature is achieved with addition of a minimum of 13% chromium. The chromium forms a layer of chromium oxide when exposed to oxygen. The layer is too thin to be visible, and the metal remains lustrous, the layer is impervious to water and air, protecting the metal beneath, and this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, corrosion resistance can be adversely affected if the component is used in a non-oxygenated environment, a typical example being underwater keel bolts buried in timber. When stainless steel parts such as nuts and bolts are forced together, when forcibly disassembled, the welded material may be torn and pitted, a destructive effect known as galling. Galling can be avoided by the use of materials for the parts forced together, for example bronze and stainless steel. However, two different alloys electrically connected in a humid, even mildly acidic environment may act as a voltaic pile, nitronic alloys, made by selective alloying with manganese and nitrogen, may have a reduced tendency to gall. Additionally, threaded joints may be lubricated to provide a film between the two parts and prevent galling, low-temperature carburizing is another option that virtually eliminates galling and allows the use of similar materials without the risk of corrosion and the need for lubrication
33.
Screw driver
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A screwdriver is a tool, manual or powered, for turning screws. A typical simple screwdriver has a handle and a shaft, the shaft is usually made of tough steel to resist bending or twisting. The tip may be hardened to resist wear, treated with a dark tip coating for improved visual contrast between tip and screw—or ridged or treated for additional grip. Handles are typically wood, metal, or plastic and usually hexagonal, square, or oval in cross-section to improve grip, some manual screwdrivers have interchangeable tips that fit into a socket on the end of the shaft and are held in mechanically or magnetically. These often have a handle that contains various types and sizes of tips. A screwdriver is classified by its tip, which is shaped to fit the driving surfaces—slots, grooves, recesses, proper use requires that the screwdrivers tip engage the head of a screw of the same size and type designation as the screwdriver tip. Screwdriver tips are available in a variety of types and sizes. The two most common are the simple blade-type for slotted screws, and Phillips®, generically referred to as cross-recess and this is particularly useful as drilling a pilot hole before driving a screw is a common operation. Special combination drill-driver bits and adapters let an operator rapidly alternate between the two, variations include impact drivers, which provide two types of hammering force for improved performance in certain situations, and right-angle drivers for use in tight spaces. Many options and enhancements, such as built-in bubble levels, high/low gear selection, magnetic screw holders, adjustable-torque clutches, keyless chucks, gyroscopic control, the earliest documented screwdrivers were used in Europe in the late Middle Ages. They were probably invented in the late 15th century, either in Germany or France, the tools original names in German and French were Schraubendreher and tournevis, respectively. The first documentation of the tool is in the medieval Housebook of Wolfegg Castle and these earliest screwdrivers had pear-shaped handles and were made for slotted screws. The screwdriver remained inconspicuous, however, as evidence of its existence throughout the next 300 years is based primarily on the presence of screws, screws, hence screwdrivers, were not used in full combat armor, most likely to give the wearer freedom of movement. The jaws that hold the pyrites inside medieval guns were secured with screws, the tool is more documented in France, and took on many shapes and sizes, though all for slotted screws. There were large, heavy-duty screwdrivers for building and repairing large machines, the screwdriver depended entirely on the screw, and it took several advances to make the screw easy enough to produce to become popular and widespread. The most popular door hinge at the time was the butt-hinge, the butt-hinge was handmade, and its constant motion required the security of a screw. Screws were very hard to produce before the First Industrial Revolution, the brothers Job and William Wyatt found a way to produce a screw on a novel machine that first cut the slotted head, and then cut the helix. Though their business failed, their contribution to low-cost manufacturing of the screw ultimately led to a vast increase in the screw
34.
Handle
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A handle is a part of, or attachment to, an object that can be moved or used by hand. The design of type of handle involves substantial ergonomic issues. Handles for tools are an important part of their function, enabling the user to exploit the tools to maximum effect, the three nearly universal requirements of are, Sufficient strength to support the object, or to otherwise transmit the force involved in the task the handle serves. Sufficient length to permit the hand or hands gripping it to exert that force. Sufficiently small circumference to permit the hand or hands to surround it far enough to grip it as solidly as needed to exert that force. Other requirements may apply to specific handles, A sheath or coating on the handle that provides friction against the hand, designs such as recessed car-door handles, reducing the chance of accidental operation, or simply the inconvenience of snagging the handle. Sufficient circumference to distribute the force comfortably and safely over the hand, design to thwart unwanted access, for example, by children or thieves. In these cases many of the requirements may have reduced importance. For example, a child-proof doorknob can be difficult for even an adult to use, one major category of handles are pull handles, where one or more hands grip the handle or handles, and exert force to shorten the distance between the hands and their corresponding shoulders. The three criteria stated above are universal for pull handles, many pull handles are for lifting, mostly on objects to be carried. Horizontal pull handles are widespread, including drawer pulls, handles on latchless doors, the inside controls for opening car doors from inside are usually pull handles, although their function of permitting the door to be pushed open is accomplished by an internal unlatching linkage. Pull handles are also a frequent host of common door handle bacteria such as e-coli, some throwing motions, as in a track-and-field hammer throw, involve pulling on a handle against centrifugal force, in the course of accelerating the thrown object by forcing it into circular motion. Another category of hand-operated device requires grasping and rotating the hand and either the arm or the whole arm. When the grip required is a fist grip, as with a handle that has an arm rather than a knob to twist
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Torque
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Torque, moment, or moment of force is rotational force. Just as a force is a push or a pull. Loosely speaking, torque is a measure of the force on an object such as a bolt or a flywheel. For example, pushing or pulling the handle of a wrench connected to a nut or bolt produces a torque that loosens or tightens the nut or bolt, the symbol for torque is typically τ, the lowercase Greek letter tau. When it is called moment of force, it is denoted by M. The SI unit for torque is the newton metre, for more on the units of torque, see Units. This article follows US physics terminology in its use of the word torque, in the UK and in US mechanical engineering, this is called moment of force, usually shortened to moment. In US physics and UK physics terminology these terms are interchangeable, unlike in US mechanical engineering, Torque is defined mathematically as the rate of change of angular momentum of an object. The definition of states that one or both of the angular velocity or the moment of inertia of an object are changing. Moment is the term used for the tendency of one or more applied forces to rotate an object about an axis. For example, a force applied to a shaft causing acceleration, such as a drill bit accelerating from rest. By contrast, a force on a beam produces a moment, but since the angular momentum of the beam is not changing. Similarly with any force couple on an object that has no change to its angular momentum and this article follows the US physics terminology by calling all moments by the term torque, whether or not they cause the angular momentum of an object to change. The concept of torque, also called moment or couple, originated with the studies of Archimedes on levers, the term torque was apparently introduced into English scientific literature by James Thomson, the brother of Lord Kelvin, in 1884. A force applied at an angle to a lever multiplied by its distance from the levers fulcrum is its torque. A force of three newtons applied two metres from the fulcrum, for example, exerts the same torque as a force of one newton applied six metres from the fulcrum. More generally, the torque on a particle can be defined as the product, τ = r × F, where r is the particles position vector relative to the fulcrum. Alternatively, τ = r F ⊥, where F⊥ is the amount of force directed perpendicularly to the position of the particle, any force directed parallel to the particles position vector does not produce a torque
36.
Microwave
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Microwaves are a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter, with frequencies between 300 MHz and 300 GHz. Different sources define different frequency ranges as microwaves, the broad definition includes both UHF and EHF bands. A more common definition in radio engineering is the range between 1 and 100 GHz, in all cases, microwaves include the entire SHF band at minimum. Frequencies in the range are often referred to by their IEEE radar band designations, S, C, X, Ku, K, or Ka band. The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range and it indicates that microwaves are small, compared to waves used in typical radio broadcasting, in that they have shorter wavelengths. The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study. At the high end of the band they are absorbed by gases in the atmosphere, microwaves are extremely widely used in modern technology. Although at the low end of the band they can pass through building walls enough for useful reception, therefore on the surface of the Earth microwave communication links are limited by the visual horizon to about 30 -40 miles. Microwaves are absorbed by moisture in the atmosphere, and the attenuation increases with frequency, beginning at about 40 GHz, atmospheric gases also begin to absorb microwaves, so above this frequency microwave transmission is limited to a few kilometers. A spectral band structure causes absorption peaks at specific frequencies, in a microwave beam directed at an angle into the sky, a small amount of the power will be randomly scattered as the beam passes through the troposphere. A sensitive receiver beyond the horizon with a high gain antenna focused on that area of the troposphere can pick up the signal. This technique has been used at frequencies between 0.45 and 5 GHz in tropospheric scatter communication systems to communicate beyond the horizon and their short wavelength allows narrow beams of microwaves to be produced by conveniently small high gain antennas from a half meter to 5 meters in diameter. Therefore beams of microwaves are used for point-to-point communication links, an advantage of narrow beams is that they allow frequency reuse by nearby transmitters. Parabolic antennas are the most widely used directive antennas at microwave frequencies, flat microstrip antennas are being increasingly used in consumer devices. Where omnidirectional antennas are required, for example in wireless devices and Wifi routers for wireless LANs, small monopoles, dipole, or patch antennas are used. Due to the high cost and maintenance requirements of waveguide runs, the term microwave also has a more technical meaning in electromagnetics and circuit theory. As a consequence, practical microwave circuits tend to away from the discrete resistors, capacitors. Open-wire and coaxial transmission lines used at lower frequencies are replaced by waveguides and stripline, high-power microwave sources use specialized vacuum tubes to generate microwaves
37.
Differential signaling
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Differential signaling is a method for electrically transmitting information using two complementary signals. The technique sends the same signal as a differential pair of signals. The pair of conductors can be wires or traces on a circuit board, the receiving circuit responds to the electrical difference between the two signals, rather than the difference between a single wire and ground. The opposite technique is called single-ended signaling, Differential pairs are usually found on printed circuit boards, in twisted-pair and ribbon cables, and in connectors. Provided that the source and receiver impedances in the signaling circuit are equal, external electromagnetic interference tends to affect both conductors identically. Since the receiving circuit detects the difference between the wires, the technique resists electromagnetic noise compared to one conductor with an un-paired reference. The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB. The electronics industry, particularly in portable and mobile devices, continually strives to supply voltage to save power. A low supply voltage, however, reduces noise immunity, Differential signaling helps to reduce these problems because, for a given supply voltage, it provides twice the noise immunity of a single-ended system. To see why, consider a digital system with supply voltage V S. The high logic level is V S and the low level is 0 V. The difference between the two levels is therefore V S −0 V = V S, now consider a differential system with the same supply voltage. The voltage difference in the state, where one wire is at V S. The voltage difference in the low state, where the voltages on the wires are exchanged, is 0 V − V S = − V S, the difference between high and low logic levels is therefore V S − =2 V S. This is twice the difference of the single-ended system, if the voltage noise on one wire is uncorrelated to the noise on the other one, it takes twice as much noise to cause an error with the differential system as with the single-ended system. In other words, differential signalling doubles the noise immunity and this advantage is not directly due to differential signaling itself, but to the common practice of transmitting differential signals on balanced lines. Single-ended signals are still resistant to interference if the lines are balanced and terminated by a differential amplifier, in single-ended signaling, the transmitter generates a single voltage that the receiver compares with a fixed reference voltage, both relative to a common ground connection shared by both ends. In many instances single-ended designs are not feasible, another difficulty is the electromagnetic interference that can be generated by a single-ended signaling system that attempts to operate at high speed
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