2013年1月4日星期五

Description of a Dispatcher’s Two-Way Radio

General Description
Two-way communications means that a device can both transmit and receive broadcast signals. These devices, known as transceivers, transmit and receive through radio frequencies assigned by the FCC through the General Mobile Radio Service (Reference 1). A typical dispatcher two-way radio system will be assigned a frequency, either in very high frequency (VHF) or ultra high frequency (UHF) sufficient to carry over small and large distances.
Conventional Two-Way
Most dispatcher 2 way radio systems are half-duplex, meaning that a push-to-talk button must be activated to be able to transmit a signal. A dispatcher two-way radio system can include more than one channel, if the equipment being used allows it. A repeater, or base station, is necessary to receive the signals from remote devices, such as hand-held walkie talkies or radio units.
Dispatcher Transmissions
In the past, most two-way systems included a transmitting device, such as a microphone, with a push-to-talk button. Later variations include a foot-operated switch that opened the channel by stepping on it and voice-activated transmitting (VOX) that automatically sends the transmission when the dispatcher speaks. This type typically includes a microphone and headset combination for hands-free use.
Analog Vs. Digital
Analog two-way radio systems are the most basic type and are often used for simple transmission of activation signals. Modern dispatcher systems are digital, which provides a wider range of broadcasting choices. Both voice and text messages are part of this spectrum. As long as the proper devices are being used, a dispatcher can send either a voice signal or a text message to a remote unit.
Choosing Frequencies
The broadcasting capacities for two-way radio systems are defined by the needs of the user. VHF signals are best for broadcasting over larger distances, whereas UHF signals are better for strong signals in a more limited area.

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