Coaxial
In geometry, coaxial means that two or more three-dimensional linear forms share a common axis. Thus, it is concentric in linear forms. A coaxial cable, as a common example, is a three-dimensional linear structure, it has a wire conductor in the centre, a circumferential outer conductor, an insulating medium called the dielectric separating these two conductors. The outer conductor is sheathed in a protective PVC outer jacket. All these have a common axis; the dimension and material of the conductors and insulation determine the cable's characteristic impedance and attenuation at various frequencies. In loudspeaker design, coaxial speakers are a loudspeaker system in which the individual driver units radiate sound from the same point or axis. A coaxial weapon mount places two weapons on the same axis – as the weapons are side-by-side or one on top of the other, they are technically par-axial rather than coaxial, however the distances involved mean that they are coaxial as far as the operator is concerned
Avionics
Avionics are the electronic systems used on aircraft, artificial satellites, spacecraft. Avionic systems include communications, the display and management of multiple systems, the hundreds of systems that are fitted to aircraft to perform individual functions; these can be as simple as a searchlight for a police helicopter or as complicated as the tactical system for an airborne early warning platform. The term avionics is a portmanteau of 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 commonplace today began as specialized systems to help bomber planes fly enough to hit precision targets from high altitudes. Famously, radar was developed in the UK, the United States during the same period. Modern avionics is a substantial portion of military aircraft spending. Aircraft like the F‑15E and the now retired F‑14 have 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 primary method of transportation, more elaborate methods of controlling aircraft safely in these high restrictive airspaces have been invented. Avionics plays a heavy role in modernization initiatives like the Federal Aviation Administration's Next Generation Air Transportation System project in the United States and the Single European Sky ATM Research initiative in Europe; the Joint Planning and Development Office put forth a roadmap for avionics in six areas: Published Routes and Procedures – Improved navigation and routing Negotiated Trajectories – Adding data communications to create preferred routes dynamically Delegated Separation – Enhanced situational awareness in the air and on the ground LowVisibility/CeilingApproach/Departure – Allowing operations with weather constraints with less ground infrastructure Surface Operations – To increase safety in approach and departure ATM Efficiencies – Improving the ATM process The Aircraft Electronics Association reports $1.73 billion avionics sales for the first three quarters of 2017 in business and general aviation, a 4.1% yearly improvement: 73.5% came from North America, forward-fit represented 42.3% while 57.7% were retrofits as the U.
S. deadline of Jan. 1, 2020 for mandatory ADS-B out approach. The cockpit of an aircraft is a typical location for avionic equipment, including control, communication, navigation and anti-collision systems; the majority of aircraft power their avionics using 14- or 28‑volt DC electrical systems. There are several major vendors of flight avionics, including Panasonic Avionics Corporation, Universal Avionics Systems Corporation, Rockwell Collins, Thales Group, GE Aviation Systems, Raytheon, Parker Hannifin, UTC Aerospace Systems and Avidyne Corporation. International standards for avionics equipment are prepared by the Airlines Electronic Engineering Committee and published by ARINC. Communications connect the flight deck to the flight deck to the passengers. On‑board communications are provided by public-address 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 used for line of sight communication such as aircraft-to-aircraft and aircraft-to-ATC. Amplitude modulation is used, the conversation is performed in simplex mode. Aircraft communication can take place using HF or satellite communication. Air navigation is the determination of position and direction above the surface of the Earth. Avionics can use satellite navigation systems, INS, ground-based radio navigation systems, or any combination thereof. Navigation systems calculate the position automatically and display it to the flight crew on moving map displays. Older avionics required a pilot or navigator to plot the intersection of signals on a paper map to determine an aircraft's location; the first hints of glass cockpits emerged in the 1970s when flight-worthy cathode ray tube screens began to replace electromechanical displays and instruments. A "glass" cockpit refers to the use of computer monitors instead of gauges and other analog displays. Aircraft were getting progressively more displays and information dashboards that competed for space and pilot attention.
In the 1970s, the average aircraft had more than 100 cockpit controls. Glass cockpits started to come into being with the Gulfstream G‑IV private jet in 1985. One of the key challenges in glass cockpits is to balance how much control is automated and how much the pilot should do manually, they try to automate flight operations while keeping the pilot informed. Aircraft have means of automatically controlling flight. Autopilot was first invented by Lawrence Sperry during World War I to fly bomber planes steady enough to hit accurate
Carl Concelman
Carl Concelman was the electrical engineer who, while working for Amphenol, invented the C connector and teamed up with Paul Neill of Bell Labs to invent the BNC connector and TNC connector. RF connector Paul Neill
Radio
Radio is the technology of signalling or communicating using radio waves. Radio waves are electromagnetic waves of frequency between 300 gigahertz, they are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, received by a radio receiver connected to another antenna. Radio is widely used in modern technology, in radio communication, radio navigation, remote control, remote sensing and other applications. In radio communication, used in radio and television broadcasting, cell phones, two-way radios, wireless networking and satellite communication among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal in the transmitter. In radar, used to locate and track objects like aircraft, ships and missiles, a beam of radio waves emitted by a radar transmitter reflects off the target object, the reflected waves reveal the object's location. In radio navigation systems such as GPS and VOR, a mobile receiver receives radio signals from navigational radio beacons whose position is known, by measuring the arrival time of the radio waves the receiver can calculate its position on Earth.
In wireless remote control devices like drones, garage door openers, keyless entry systems, radio signals transmitted from a controller device control the actions of a remote device. Applications of radio waves which do not involve transmitting the waves significant distances, such as RF heating used in industrial processes and microwave ovens, medical uses such as diathermy and MRI machines, are not called radio; the noun radio is used to mean a broadcast radio receiver. Radio waves were first identified and studied by German physicist Heinrich Hertz in 1886; the first practical radio transmitters and receivers were developed around 1895-6 by Italian Guglielmo Marconi, radio began to be used commercially around 1900. To prevent interference between users, the emission of radio waves is regulated by law, coordinated by an international body called the International Telecommunications Union, which allocates frequency bands in the radio spectrum for different uses. Radio waves are radiated by electric charges undergoing acceleration.
They are generated artificially by time varying electric currents, consisting of electrons flowing back and forth in a metal conductor called an antenna. In transmission, a transmitter generates an alternating current of radio frequency, applied to an antenna; the antenna radiates the power in the current as radio waves. When the waves strike the antenna of a radio receiver, they push the electrons in the metal back and forth, inducing a tiny alternating current; the radio receiver connected to the receiving antenna detects this oscillating current and amplifies it. As they travel further from the transmitting antenna, radio waves spread out so their signal strength decreases, so radio transmissions can only be received within a limited range of the transmitter, the distance depending on the transmitter power, antenna radiation pattern, receiver sensitivity, noise level, presence of obstructions between transmitter and receiver. An omnidirectional antenna transmits or receives radio waves in all directions, while a directional antenna or high gain antenna transmits radio waves in a beam in a particular direction, or receives waves from only one direction.
Radio waves travel through a vacuum at the speed of light, in air at close to the speed of light, so the wavelength of a radio wave, the distance in meters between adjacent crests of the wave, is inversely proportional to its frequency. In radio communication systems, information is carried across space using radio waves. At the sending end, the information to be sent is converted by some type of transducer to a time-varying electrical signal called the modulation signal; the modulation signal may be an audio signal representing sound from a microphone, a video signal representing moving images from a video camera, or a digital signal consisting of a sequence of bits representing binary data from a computer. The modulation signal is applied to a radio transmitter. In the transmitter, an electronic oscillator generates an alternating current oscillating at a radio frequency, called the carrier wave because it serves to "carry" the information through the air; the information signal is used to modulate the carrier, varying some aspect of the carrier wave, impressing the information on the carrier.
Different radio systems use different modulation methods: AM - in an AM transmitter, the amplitude of the radio carrier wave is varied by the modulation signal. FM - in an FM transmitter, the frequency of the radio carrier wave is varied by the modulation signal. FSK - used in wireless digital devices to transmit digital signals, the frequency of the carrier wave is shifted periodically between two frequencies that represent the two binary digits, 0 and 1, to transmit a sequence of bits. OFDM - a family of complicated digital modulation methods widely used in high bandwidth systems such as WiFi networks, digital television broadcasting, digital audio broadcasting to transmit digital data using a minimum of radio spectrum bandwidth. OFDM has higher spectral efficiency and more resistance to fading than AM or FM. Multiple radio carrier waves spaced in frequency are transmitted within the radio channel, with each carrier modulated with bits from the incoming bitstream
Electrical termination
In electronics, electrical termination is the practice of ending a transmission line with a device that matches the characteristic impedance of the line. This is intended to prevent signals from reflecting off the end of the transmission line. Reflections at the ends of unterminated transmission lines cause distortion which can produce ambiguous digital signal levels and mis-operation of digital systems. Reflections in analog signal systems cause such effects as video ghosting, or power loss in radio transmitter transmission lines. Signal termination requires the installation of a terminator at the beginning and end of a wire or cable to prevent an RF signal from being reflected back from each end, causing interference, or power loss; the terminator is placed at the end of a transmission line or daisy chain bus, is designed to match the AC impedance of the cable and hence minimize signal reflections, power losses. Less a terminator is placed at the driving end of the wire or cable, if not part of the signal-generating equipment.
Radio frequency currents tend to reflect from discontinuities in the cable such as connectors and joints, travel back down the cable toward the source causing interference as primary reflections. Secondary reflections can occur at the cable start, allowing interference to persist as repeated echoes of old data; these reflections 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; the distinguishing feature of most transmission line cables is that they have uniform cross sectional dimensions along their length, giving them a uniform electrical characteristic impedance. Signal terminators are designed to match the characteristic impedances at both cable ends. For many systems, the terminator is a resistor, with a value chosen to match the characteristic impedance of the transmission line, chosen to have acceptably low parasitic inductance and capacitance at the frequencies relevant to the system.
Examples include 75 ohm resistors used to terminate 75-ohm video transmission coaxial cables. Types of transmission line cables include balanced line such as ladder line, twisted pairs. Passive terminators consist of a single resistor, however reactive loads may require other passive components such as inductors, capacitors, or transformers. Active terminators consist of a voltage regulator that keeps the voltage used for the terminating resistor at a constant level. Forced perfect termination can be used on single ended buses where diodes remove over and undershoot conditions; the signal is locked between two regulated voltage levels, which results in superior performance over a standard active terminator. All parallel SCSI units use terminators. SCSI is used for storage and backup. An active terminator is a type of single ended SCSI terminator with a built-in voltage regulator to compensate for variations in terminator power. Controller area network known as CAN Bus, uses terminators consisting of a 120 ohm resistor.
Dummy loads are used in HF to EHF frequency circuits. 10BASE2 networks must have proper termination with a 50 ohm BNC terminator. If the bus network is not properly terminated, too much power will be reflected, causing all of the computers on the bus to lose network connectivity. A terminating resistor for a television coaxial cable is in the form of a cap, threaded to screw onto an F connector. Antenna cables are sometimes used for internet connections; the Digital Equipment Corporation minicomputer Unibus systems used terminator cards with 178 Ω pullup resistors on the multi-drop address and data lines, 383 Ω on the single-drop signal lines. Terminating resistors values of 78.7 ohms. At the two ends of the bus, resistors connect between the positive and negative signal wires either in internally terminated bus couplers or external connectorized terminators; the MIL-STD-1553B bus must be terminated at both ends to minimize the effects of signal reflections that can cause waveform distortion and disruption or intermittent communications failures.
Optionally, a high-impedance terminator may be used in vehicle applications to simulate a future load from an unspecified device. Connectorized terminators are available without safety chains. Electrical connector Electrical network MIL-STD-1553 Telecommunications pedestal Signal reflection Impedance matching Biasing Pothead for a termination on a high voltage electric power cable
Handle
A handle is a part of, or attachment to, an object that can be moved or used by hand. The design of each type of handle involves substantial ergonomic issues where these are dealt with intuitively or by following tradition. Handles for tools are an important part of their function, enabling the user to exploit the tools to maximum effect. Package handles allow for convenient carrying of packages; 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 reliably 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, reducing the gripping force needed to achieve a reliable grip. Designs such as recessed car-door handles, reducing the chance of accidental operation, or the inconvenience of "snagging" the handle.
Sufficient circumference to safely over the hand. An example where this requirement is the sole purpose for a handle's existence is the handle that consists of two pieces: a hollow wooden cylinder about the diameter of a finger and a bit longer than one hand-width, a stiff wire that passes through the center of the cylinder, has two right angles, is shaped into a hook at each end; this handle permits comfortable carrying, with otherwise bare hands, of a heavy package, suspended on a tight string that passes around the top and bottom of it: the string is strong enough to support it, but the pressure the string would exert on fingers that grasped it directly would be unacceptable. Design to thwart unwanted access, for example, by thieves. In these cases many of the other requirements may have reduced importance. For example, a child-proof doorknob can be difficult for an adult to use. One major category of handles are pull handles, where one or more hands grip the handle or handles, 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 on objects to be carried. Horizontal pull handles are widespread, including drawer pulls, handles on latchless doors and the outside of car doors; the inside controls for opening car doors from inside are pull handles, although their function of permitting the door to be pushed open is accomplished by an internal unlatching linkage. Pull handles are a frequent host of common door handle bacteria such as e-coli, fungal or other viral infections. Two kinds of pull handles may involve motion in addition to the hand-focused motions described: Pulling the starting cord on a small internal-combustion engine may, besides moving the hand toward the shoulder exploit pushing a wheeled vehicle away with the other hand, stepping away from the engine, and/or standing from a squat; 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 lower arm or the whole arm, about their axis. When the grip required is a fist grip, as with a door handle that has an arm rather than a knob to twist, the term "handle" unambiguously applies. Another clear case is a rarer device seen on mechanically complicated doors like those of airliners, where the axis of rotation is between the thumb and the outermost fingers, so the thumb moves up if the outer fingers move down; the handles of bicycle grips, club-style weapons and spades, hammers and hatchets, baseball bats, golf clubs, croquet mallets involve a greater range of ergonomic issues
ARCNET
Attached Resource Computer NETwork is a communications protocol for local area networks. ARCNET was the first available networking system for microcomputers, it was applied to embedded systems where certain features of the protocol are useful. ARCNET was developed by principal development engineer John Murphy at Datapoint Corporation in 1976 under Victor Poor, announced in 1977, it was developed to connect groups of their Datapoint 2200 terminals to talk to a shared 8" floppy disk system. It was the first loosely coupled LAN-based clustering solution, making no assumptions about the type of computers that would be connected; this was in contrast to contemporary larger and more expensive computer systems such as DECnet or SNA, where a homogeneous group of similar or proprietary computers were connected as a cluster. The token-passing bus protocol of that I/O device-sharing network was subsequently applied to allowing processing nodes to communicate with each other for file-serving and computing scalability purposes.
An application could be developed in DATABUS, Datapoint's proprietary COBOL-like language and deployed on a single computer with dumb terminals. When the number of users outgrew the capacity of the original computer, additional'compute' resource computers could be attached via ARCNET, running the same applications and accessing the same data. If more storage was needed, additional disk resource computers could be attached; this incremental approach broke new ground and by the end of the 1970s over ten thousand ARCNET LAN installations were in commercial use around the world, Datapoint had become a Fortune 500 company. As microcomputers took over the industry, well-proven and reliable ARCNET was offered as an inexpensive LAN for these machines. ARCNET remained proprietary until the early-to-mid 1980s; this did not cause concern at the time. The move to non-proprietary, open systems began as a response to the dominance of International Business Machines and its Systems Network Architecture. In 1979, the Open Systems Interconnection Reference Model was published.
In 1980, Digital and Xerox published an open standard for Ethernet, soon adopted as the basis of standardization by the IEEE and the ISO. IBM responded by proposing Token ring as an alternative to Ethernet but kept such tight control over standardization that competitors were wary of using it. ARCNET was less expensive than either, more reliable, more flexible, by the late 1980s it had a market share about equal to that of Ethernet. Tandy/Radio Shack offered ARCNET as an application and file sharing medium for their TRS-80 Model II, Model 12, Model 16, Tandy 6000, Tandy 2000, Tandy 1000 and Tandy 1200 computer models. There were hooks in the Model 4P's ROM to boot from an ARCNET network; when Ethernet moved from co-axial cable to twisted pair and an "interconnected stars" cabling topology based on active hubs, it became much more attractive. Easier cabling, combined with the greater raw speed of Ethernet helped to increase Ethernet demand, as more companies entered the market the price of Ethernet started to fall—and ARCNET volumes tapered off.
In response to greater bandwidth needs, the challenge of Ethernet, a new standard called ARCnet Plus was developed by Datapoint, introduced in 1992. ARCnet Plus ran at 20 Mbit/s, was backward compatible with original ARCnet equipment. However, by the time ARCnet Plus products were ready for the market, Ethernet had captured the majority of the network market, there was little incentive for users to move back to ARCnet; as a result few ARCnet Plus products were produced. Those that were built by Datapoint, were expensive, hard to find. ARCNET was standardized as ANSI ARCNET 878.1. It appears this was when the name changed from ARCnet to ARCNET. Other companies entered the market, notably Standard Microsystems who produced systems based on a single VLSI chip developed as custom LSI for Datapoint, but made available by Standard Microsystems to other customers. Datapoint found itself in financial trouble and moved into video conferencing and custom programming in the embedded market. Though ARCNET is now used for new general networks, the diminishing installed base still requires support - and it retains a niche in industrial control.
Original ARCNET used RG-62/U coaxial cable of 93 Ω impedance and either passive or active hubs in a star-wired bus topology. At the time of its greatest popularity, this was a significant advantage of ARCNET over Ethernet. A star-wired bus was much easier to build and expand than the clumsy linear bus Ethernet of the time; the "interconnected stars" cabling topology made it easy to add and remove nodes without taking down the whole network, much easier to diagnose and isolate failures within a complex LAN. Another significant advantage ARCNET had over Ethernet was cable distance. ARCNET coax cable runs could extend 610 m between active hubs or between an active hub and an end node, while the RG-58'thin' Ethernet most used at that time was limited to a maximum run of 180 m from end to end. ARCNET had the disadvantage of requiring either an active or passive hub between nodes if there were more than two nodes in the network, while thin Ethernet allowed nodes to be spaced anywhere along the linear coax cable.
However, ARCNET passive hubs were inexpensive, being composed of a simple
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