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184:). The system commonly uses an analog power amplifier matched to the low impedance of the transmission loop. The transmission is normally direct rather than superimposed or modulated upon a carrier, though multi-channel systems have been implemented using modulation. Many hearing aids contain a telecoil which allows the user to receive and hear the magnetic field and remove the normal audio signal provided from the hearing aid microphone site.
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sometimes also means that bicycles, scooters, and motorcycles stopped at such intersections may be undetected (and therefore risk being ignored by the switch/signal). Most loops can be adjusted manually to consistently detect the presence of scooters and motorcycles. Several U.S. states have enacted "dead red" laws which permit such vehicles to proceed through a red signal after a given time if the loop does not detect them.
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to 200 kHz, depending on the model. The inductive-loop system behaves as a tuned electrical circuit in which the loop wire and lead-in cable are the inductive elements. When a vehicle passes over the loop or is stopped within the loop, some of the vehicle's ferrous body material increases the
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Since there is no "tuning" available, as the telecoil directly picks up all audio-frequency magnetic fields, careful system design is required where more than one induction loop is used in a building; for example, adjacent movie theatres or lecture halls. Telecoils may also pick up noise from
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The relatively crude nature of the loop means that small metal masses cannot trigger the relay. This is good in that the loop does not thus produce very many "false positive" triggers (say, for example, by a pedestrian crossing the loop with a pocket full of loose metal change). However, it
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tends to decrease the electrical impedance of the wire to alternating current. The decrease in impedance actuates the electronics unit output relay or solid-state optically isolated output, which sends a pulse to the traffic signal controller signifying the passage or presence of a vehicle.
153:/cavity detection). Other configurations of this equipment use two or more receiving coils, and the detected object modifies the inductive coupling or alters the phase angle of the voltage induced in the receiving coils relative to the oscillator coil.
180:, also known as a hearing loop, provides assistance to hearing aid users. The system has one or more loops in the area in which a hearing aid user would be present. Such an induction loop receiver is classically a very small iron-cored inductor (
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are used for transmission and reception of communication signals, or for detection of metal objects in metal detectors or vehicle presence indicators. A common modern use for induction loops is to provide hearing assistance to hearing-aid users.
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that are produced. The decrease in inductance from the eddy currents more than offsets the increase from the ferrous mass of the engine, and the net effect is an overall reduction in the inductance of the wire loop. The decrease in
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or in motorway traffic. An insulated, electrically conducting loop is installed in the pavement. The electronics unit applies alternating current electrical energy onto the wire loops at frequencies between 10
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Inductance loops have also been used to classify types of vehicles. Sampling the loop at a high frequency results in a unique signature for each vehicle allowing for classification of the body type.
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Parking structures for automobiles may use inductive loops to track traffic (occupancy) in and out or may be used by access gates or ticketing systems to detect vehicles while others use
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loop's inductance, in the same principle as including a metal core within a solenoid coil. However, the peripheral metal of the vehicle has an opposite effect on the inductance due to
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Loop and infrared systems - for deaf and hard of hearing people (fact sheet) A practical guide from the Royal
National Institute for the Deaf in the UK.
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systems. Railways may use an induction loop to detect the passage of trains past a given point, as an electronic
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273:"How motorcyclists can run red lights for Bike Week in Myrtle Beach area. What SC law says"
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This article is about a detection system. For the more general electrical component, see
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and surface vessels using specially designed submerged cables connected to a
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An example of the inductance loop installed in the road for cars and bikes
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non-audio sources such as power lines, lamps, or CRT monitors.
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Samuel R. Atcherson, Clifford A. Franklin, Laura Smith-Olinde
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communication or detection system which uses a moving
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330:"What are Indicator Loops and how do they work?"
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208:Sydney Coordinated Adaptive Traffic System
355:Hearing Assistive and Access Technology
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317:from the original on 2021-12-13.
252:. Federal Highway Administration
119:parking guidance and information
92:inductive-loop traffic detectors
90:Vehicle detection loops, called
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158:anti-submarine indicator loop
42:or an alternating current to
305:"Inductance Loop Signatures"
284:Myrtle Beach, South Carolina
270:Muzzy, Emalyn (2024-03-04).
160:was a device used to detect
80:Schematic of such a detector
357:, Plural Publishing, 2015,
250:"Traffic Detector Handbook"
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382:Electromagnetic components
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16:Type of detection system
133:Vehicle classification
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392:Assistive technology
178:audio induction loop
387:Military technology
334:Indicatorloops.com
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290:2024-03-09
256:2011-12-20
236:References
162:submarines
111:inductance
84:See also:
28:induction
315:Archived
192:See also
182:telecoil
21:Inductor
310:YouTube
123:treadle
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44:induce
40:magnet
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