SIGNALLING BLANKING FOR ANALOG RADIOS USING IN-BAND SIGNALLING
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2002-May-17
Some analog trunked radio communications systems that use in-band signalling techniques to transmit signalling information, e.g. MPT1327 with frequency shift keying, within the audio (speech) bandwidth via signalling tones. This signalling information is occasionally, and undesirably, audi- ble in the radio loudspeaker as noise. In MPT1327 radio units these signalling tones are generated every time the radio user presses or releases the PTT, either during call cancellation or for status request purposes.