| 摘要 |
PURPOSE:To reduce the processing volume of a central controller considerably by providing a scan pulse generating circuit and an on/off change information circuit in a subscriber's circuit and fulfilling a periodical scan control function in the subscriber's circuit. CONSTITUTION:A subscriber's circuit 1 includes a channel current supply circuit 2, a loop monitor circuit 3, and a scan period pulse generating circuit 6 and an on/off discriminating circuit 7 which are interposed between the circuit 3 and a central controller 4. The controller 4 determines the scan period in accordance with the call state of a telephone 5, and the circuit 6 receives scan period information (c) from the controller 4 and transmits a driving signal (d) to the loop monitor circuit 3 at a prescribed period on a basis of this information (c). The circuit 3 transmits a monitor result (c) of the telephone loop to the circuit 7. When detecting the change of the telephone loop state, the circuit 6 transmits on/off change information (f) to the controller 4. Thus, the periodical scan read function reduces considerably the processing time of the circuit 3 in the subscriber's circuit. |
