| 摘要 |
PURPOSE:To realize non-metallization of a cable, by providing an order-wire telephone board to the using circuit to superpose an order-wire signal onto a main signal, and at the same time, a monitor controller to a space circuit to superpose a monitor control signal onto the main signal respectively and then transmitting both signals after superposing them with the main signal. CONSTITUTION:Transmission line changeover switches 6-1-6-n connect transmission lines after switching them to corresponding using optical transmitters 8-1- 8-n or to a spare optical transmitter 8-x at end office repeaters 3 and 4. At the same time, transmission switch devices 1 and 2 connect reception lines after switching them to corresponding using optical receivers 9-1-9-n or to a spare optical receiver 9-x through transmission line changeover switches 7-1-7-n. Here a synchronizing signal indicates the frame starting position, and a parity monitor signal is inserted to perform a parity check for each frame. Thus it is possible to superpose an order-wire signal or a monitor control signal with the same frame constitution as a main signal. |
