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4-20 MA
In electrical signalling an analog current loop is used where a device must be monitored or controlled remotely over a pair of conductors. Only one current level can be present at any time. A major application of current loops is the industry de facto standard 4–20 mA current loop for process control applications, where they are extensively used to carry signals from process instrumentation to PID controllers, SCADA systems, and programmable logic controllers (PLCs). They are also used to transmit controller outputs to the modulating field devices such as control valves. These loops have the advantages of simplicity and noise immunity, and have a large international user and equipment supplier base. Some 4–20 mA field devices can be powered by the current loop itself, removing the need for separate power supplies, and the "smart" HART protocol uses the loop for communications between field devices and controllers. Various automation protocols may replace analog cur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal (electrical Engineering)
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' includes audio, video, speech, image, sonar, and radar as examples of signal. A signal may also be defined as observable change in a quantity over space or time (a time series), even if it does not carry information. In nature, signals can be actions done by an organism to alert other organisms, ranging from the release of plant chemicals to warn nearby plants of a predator, to sounds or motions made by animals to alert other animals of food. Signaling occurs in all organisms even at cellular levels, with cell signaling. Signaling theory, in evolutionary biology, proposes that a substantial driver for evolution is the ability of animals to communicate with each other by developing ways of signaling. In human engineering, signals are typi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chart Recorder
A chart recorder is an electromechanical device that records an electrical or mechanical input trend onto a piece of paper (the chart). Chart recorders may record several inputs using different color pens and may record onto strip charts or circular charts. Chart recorders may be entirely mechanical with clockwork mechanisms, electro-mechanical with an electrical clockwork mechanism for driving the chart (with mechanical or pressure inputs), or entirely electronic with no mechanical components at all (a virtual chart recorder). Chart recorders are built in three primary formats. Strip chart recorders have a long strip of paper that is ejected out of the recorder. Circular chart recorders have a rotating disc of paper that must be replaced more often, but are more compact and amenable to being enclosed behind glass. Roll chart recorders are similar to strip chart recorders except that the recorded data is stored on a round roll, and the unit is usually fully enclosed. Chart record ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Current-to-voltage Converter
In electronics, a transimpedance amplifier (TIA) is a current to voltage converter, almost exclusively implemented with one or more operational amplifiers. The TIA can be used to amplify the current output of Geiger–Müller tubes, photo multiplier tubes, accelerometers, photo detectors and other types of sensors to a usable voltage. Current to voltage converters are used with sensors that have a current response that is more linear than the voltage response. This is the case with photodiodes where it is not uncommon for the current response to have better than 1% nonlinearity over a wide range of light input. The transimpedance amplifier presents a low impedance to the photodiode and isolates it from the output voltage of the operational amplifier. In its simplest form a transimpedance amplifier has just a large valued feedback resistor, Rf. The gain of the amplifer is set by this resistor and because the amplifier is in an inverting configuration, has a value of -Rf. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Current Source
A current source is an electronic circuit that delivers or absorbs an electric current which is independent of the voltage across it. A current source is the dual of a voltage source. The term ''current sink'' is sometimes used for sources fed from a negative voltage supply. Figure 1 shows the schematic symbol for an ideal current source driving a resistive load. There are two types. An ''independent current source'' (or sink) delivers a constant current. A ''dependent current source'' delivers a current which is proportional to some other voltage or current in the circuit. Background , - align="center" , style="padding: 1em 2em 0;", , style="padding: 1em 2em 0;", , - align="center" , Voltage source , Current source , - align="center" , style="padding: 1em 2em 0;", , style="padding: 1em 2em 0;", , - align="center" , Controlled voltage source , Controlled current source , - align="center" , style="padding: 1em 2em 0;", , style="padding: 1em 2em 0;", , - align ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dispatcher
A dispatcher is a communications worker who receives and transmits information to coordinate operations of other personnel and vehicles carrying out a service. A number of organizations, including police and fire departments, emergency medical services, motorcycle couriers, taxicab providers, trucking companies, railroads, and public utility companies, use dispatchers to relay information, direct personnel, and coordinate their operations. Types of dispatchers Emergency dispatchers An emergency dispatcher, also known as public safety dispatcher, 9-1-1 dispatcher, or public safety telecommunicator www.bls.gov ''Occupational Employment and Wages May 2020''. URL accessed on August 19, 2021 receives calls from individuals who require emergency ser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taxicab
A taxi, also known as a taxicab or simply a cab, is a type of vehicle for hire with a driver, used by a single passenger or small group of passengers, often for a non-shared ride. A taxicab conveys passengers between locations of their choice. This differs from public transport where the pick-up and drop-off locations are decided by the service provider, not by the customers, although demand responsive transport and share taxis provide a hybrid bus/taxi mode. There are four distinct forms of taxicab, which can be identified by slightly differing terms in different countries: * Hackney carriages, also known as public hire, hailed or street taxis, licensed for hailing throughout communities * Private hire vehicles, also known as minicabs or private hire taxis, licensed for pre-booking only * Taxibuses, also come in many variations throughout the developing countries as jitneys or jeepney, operating on pre-set routes typified by multiple stops and multiple independent passenger ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tone Remote
Remote controls are used any time a two-way radio base station is located away from the desk or office where communication originates. For example, a dispatch center for taxicabs may have an office downtown but have a base station on a distant mountain top. A Tone remote, also known as an EIA Tone remote, is a signaling system used to operate a two-way radio base station by some form of remote control. A tone remote may be a stand-alone desktop device in a telephone housing with a speaker where the dial would have been located. It may look like a desk top base station. Or, it may be an integral part of a computer-based console system with touch-screens in a dispatch center. History The first two-way radio remote controls utilized a harness of wires extending speaker, microphone, and controls for options such as channel selection or CTCSS switches. This limited a base station to being within tens to hundreds of feet from the user's workstation. Early systems often had volume un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base Station
Base station (or base radio station) is – according to the International Telecommunication Union's (ITU) Radio Regulations (RR) – a "land station in the land mobile service." The term is used in the context of mobile telephony, wireless computer networking and other wireless communications and in land surveying. In surveying, it is a GPS receiver at a known position, while in wireless communications it is a transceiver connecting a number of other devices to one another and/or to a wider area. In mobile telephony, it provides the connection between mobile phones and the wider telephone network. In a computer network, it is a transceiver acting as a switch for computers in the network, possibly connecting them to a/another local area network and/or the Internet. In traditional wireless communications, it can refer to the hub of a dispatch fleet such as a taxi or delivery fleet, the base of a TETRA network as used by government and emergency services or a CB shack. Land s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Signals
Traffic lights, traffic signals, or stoplights – known also as robots in South Africa are signalling devices positioned at road intersections, pedestrian crossings, and other locations in order to control flows of traffic. Traffic lights consist normally of three signals, transmitting meaningful information to drivers and riders through colours and symbols including arrows and bicycles. The regular traffic light colours are red, yellow, and green arranged vertically or horizontally in that order. Although this is internationally standardised,1968, as revised 1995 and 2006Vienna Convention on Road Signs and Signals United Nations Publication ECE/TRANS/196. ISBN 978-92-1-116973-7. URL Accessed: 7 January 2022. variations exist on national and local scales as to traffic light sequences and laws. The method was first introduced in December 1868 on Parliament Square in London to reduce the need for police officers to control traffic. Since then, electricity and computerised co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siren (noisemaker)
A siren is a loud noise-making device. Civil defense sirens are mounted in fixed locations and used to warn of natural disasters or attacks. Sirens are used on emergency service vehicles such as ambulances, police cars, and fire engines. There are two general types: mechanical and electronic. Many fire sirens (used for calling the volunteer fire fighters) serve double duty as tornado or civil defense sirens, alerting an entire community of impending danger. Most fire sirens are either mounted on the roof of a fire station or on a pole next to the fire station. Fire sirens can also be mounted on or near government buildings, on tall structures such as water towers, as well as in systems where several sirens are distributed around a town for better sound coverage. Most fire sirens are single tone and mechanically driven by electric motors with a rotor attached to the shaft. Some newer sirens are electronically driven speakers. Fire sirens are often called "fire whistles", "fir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Two-way Radio
A two-way radio is a radio that can both transmit and receive radio waves (a transceiver), unlike a broadcast receiver which only receives content. It is an audio (sound) transceiver, a transmitter and receiver in one unit, used for bidirectional person-to-person voice communication with other users with similar radios. Two-way radios are available in stationary ( base station), mobile (installed in vehicles), and hand-held portable models. Hand-held two-way radios are often called walkie-talkies, handie-talkies or hand-helds. Two-way radios are used by groups of geographically separated people who need to keep in continuous voice communication, such as aircraft pilots and air traffic controllers, ship captains and harbormasters, emergency services personnel like firefighters, police officers, and ambulance paramedics, taxi and delivery services, soldiers and military units, fast food and warehouse employees, and radio amateurs. Two-way radio systems may use a single radio c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
