| 摘要 |
<p>The remote control system having symmetrical signalling circuits for radio communications is coupled to a single wire line/audio channel (26) and permits two or more units, base stations (12) and/or remote consoles (14), to be coupled to the single wire line. Each signalling circuit comprises a wire line coupler (48) for coupling to the wire line (26), an audio input (46) line and an audio output (44) line. An automatic gain control circuit (56) is coupled between the wire coupler (48) and the audio output (44) line and a filter (104) and line driver (106) are coupled between the audio input (46) line and the wire coupler (48). A control unit (70) including a microprocessor (71), a tone encoder (214), a tone decoder (210), a timer, a clock, and a memory (212) is coupled by output lines to the automatic gain control circuit (56) for controlling the modes of operation thereof which include a slow decay mode, a fast decay mode, an adapt mode and a hold gain mode. The output from the gain control circuit (56) is also routed through a bandpass filter (64) and a limiter (67) to the control unit (70). Further, the tone encoder (214) of the control unit (70) is coupled to a summing circuit (102) situated between the filter (104) and line driver (106) through a filter (97) and level control circuit (100). The protocol programmed in the microprocessor enables any unit to take control of the audio channel (26) by initiating the sending of a message. Also mute gates (60, 80) are provided for disabling audio output or audio input while a message is being sent or received over the audio channel (26).</p> |
