| 摘要 |
A station-to-station supervision system for a telephone system has a dual tone multiple frequency (DTMF) signal generator connected to the transmit line at each subscriber station, and a standard audible signal generator is connected to the receive line at each subscriber station for generating dial tone, ringback tone, reorder tone and busy tone in response to supervisory DTMF signals. Control means associated with each subscriber station effect the generation of a dial tone disable DTMF signal from a calling station in response to the combination of an off-hook condition at the calling station and the absence of a DTMF signal from any other station in the system; a busy tone command DTMF signal from any given station in response to the combination of an address signal for that station and an off-hook condition at that station; and a ringback tone command DTMF signal from any given station in response to the combination of an address signal for that station and an on-hook condition at that station. The control means also generates a DTMF signal for terminating ringback tone at a calling station when a called station comes off-hook. The system also includes optional operating modes such as push-to-talk, conference calls, group calls, and all call.
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