| 摘要 |
PURPOSE:To reduce the power consumption as well as to secure the call at the time of the fault occurrence by installing both the working and emergency-use talking circuits plus the order telephone call device and actuating the functions of both the switch of the talking circuit and the fault detector of the working talking circuit only at the telephone call time. CONSTITUTION:Tandem offices B1 and B2 are installed between two end offices A1 and A2. In offices B1 and B2, circuit state detector 1 and switch 2 are functioned only when order telephone 3 is used in coupling to the call switch and with make of the power source, and remote supervisory signal transmitter function at all times to be inserted only to the working talking circuit via hybrid 5. At offices A1 and A2, the remote supervisory signals received are branched off via hybrid 5 and then inserted to the backward emergency talking circuit via filter 7 to be returned to other end offices. Thus the remote supervisory signals of the tandem office can be received at the end office even if the working talking circuit has some fault. As a result, in case the working talking circuit is faulty when the order telephone is used at the tandem office, an automatic switching is possible to the emergency talking circuit to secure the call. Furthermore, the oblique-lined areas in the figure are always in the cut-off state of the power supply, thus saving the power consumption. |
