| 摘要 |
PURPOSE:To recognize easily the connecting state between extensions and between an extension and a trunk by allowing a central controller to display the same serial number from a serial number providing circuit to a subscriber circuit and a track circuit at each setting of channel. CONSTITUTION:Connecting state display circuits 200-202 and 700, 701 are incorporated respectively to subscriber lines 100-102 and trunk lines 600, 601. A central control unit 400 indicates the provision of a serial number to a serial number providing circuit 500 in controlling a main channel switch circuit 300 to set a talking circuit. The circuit 500 returns the present serial number to the unit 400 and also increments the serial number by +1. When the unit 400 receives the serial number, the circuit 400 allows the display circuits of the subscriber circuits at the caller side and the called party side, or the trunk circuits or the like to display the serial number. Thus, the maintenance personnel recognizes quickly the connecting state of the line easily. |
