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Invisible Fence Inc. (commonly referred to as Invisible Fence Brand) is a company that designs radio pet fences for cats and dogs. Manufactured and distributed by Radio System Corporation, the company sells wireless and fenceless systems that were first introduced in 1973. [ 1 ]
A pet fence or radio fence, is an electronic system designed to keep a pet or other domestic animal within a set of predefined boundaries without the use of a physical barrier. A mild electric shock is delivered by an electronic collar if its warning sound is ignored.
Encoder receiver transmitter (ERT) is a packet radio protocol developed by Itron for automatic meter reading. [1] The technology is used to transmit data from utility meters over a short range so a utility vehicle can collect meter data without a worker physically inspecting each meter. The ERT protocol was first described in U.S. patent ...
WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. Transmissions carry a station's callsign, Maidenhead grid locator, and transmitter power in dBm. The program can decode signals with a signal-to-noise ratio as low as −28 dB in a 2.5 kHz bandwidth. [2]
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Fresnel zone: D is the distance between the transmitter and the receiver; r is the radius of the first Fresnel zone (n=1) at point P. P is d1 away from the transmitter, and d2 away from the receiver. The concept of Fresnel zone clearance may be used to analyze interference by obstacles near the path of a radio beam. The first zone must be kept ...
To get the voice signal to the remote transmitter, dedicated telephone lines connected these stations to Houston. NASA could either build a parallel system for operating the transmitters—one line to carry the audio and another to carry the control signal for the PTT button ( out-of-band signalling )—or combine these two systems together ...
Overview diagram of COSPAS-SARSAT communication system used to detect and locate ELTs, EPIRBs, and PLBs First generation EPIRB emergency locator beacons. An emergency position-indicating radiobeacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats, a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in need of ...