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Used for elevated base station antennas for land mobile radio systems such as police, ambulance, and taxi dispatchers. Mast radiator A radio tower in which the tower structure itself serves as the antenna. Common form of transmitting antenna for AM radio stations and other MF and LF transmitters.
Omnidirectional antennas are widely used for radio broadcasting antennas, [3] and in mobile devices that use radio such as cell phones, FM radios, walkie-talkies, wireless computer networks, cordless phones, GPS, as well as for base stations that communicate with mobile radios, such as police and taxi dispatchers and aircraft communications.
The Foster scanner consists of two parts; a box-shaped antenna and the "scanner" itself. These are normally placed in front of a shaped reflector.. The antenna consists of a thin rectangular section of a parabolic antenna, as if one cut the sides away from a conventional parabolic antenna, leaving only the thin strip where the feed horn is mounted.
Several hand-held Project 25 radios used around the world. Project 25 (P25 or APCO-25) is a suite of standards for interoperable digital two-way radio products. P25 was developed by public safety professionals in North America and has gained acceptance for public safety, security, public service, and commercial applications worldwide. [1]
An Icom IC-R5 hand-held scanner A GMRS radio that also has scanning capabilities. A scanner (also referred to as a radio scanner) is a radio receiver that can automatically tune, or scan, two or more discrete frequencies, stopping when it finds a signal on one of them and then continuing to scan other frequencies when the initial transmission ceases.
Slotted array UHF television broadcasting antenna. As shown by H. G. Booker in 1946, from Babinet's principle in optics a slot in a metal plate or waveguide has the same radiation pattern as a driven rod antenna whose rod is the same shape as the slot, with the exception that the electric field and magnetic field directions are interchanged; the antenna is a magnetic dipole instead of an ...
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A voice-activated radio-dispatched alarm, or VARDA-alarm, is a type of burglar alarm that, when activated or "tripped", broadcasts the type of the alarm and the transmitter location over the local police radio frequency using a pre-recorded audio message. [1] In 1968, the voice-activated radio dispatched alarm (VARDA), was invented.