| 摘要 |
PURPOSE:To monitor a failure of subscriber lines at all times, by providing a means monitoring a channel current supply power source of an exchange at all times for a signal relay device. CONSTITUTION:Signal relay devices 11-14 are connected in a loop, and the device 11 and the exchange 1 are connected with a subscriber line (a). The other relay devices are connected to a telephone set 2 via a line (b). A channel current supply source monitor circuit is provided in the device 11, consists of diodes D1-D4, a light emitting diode P1, a photo transistor P2, and a relay 5, and terminals 3, 4 are connected to both ends of the line (a). When the line (a) is normal, the P1 keeps illumination independently of calls and the relay 5 is activated. Thus, if the line (a) is failed, the relay 5 is restored. This failure information is given to each signal relay device via a loop transmission line (c). |
