| 摘要 |
PURPOSE:To switch a circuit automatically when a fault occurs to the circuit by providing a receiving switch switching circuit which operates a changeover switch to a stand-by receiving circuit by a step-out detection signal from a multiplex modem unit when a fault occurs to an in-use receiving circuit. CONSTITUTION:If a fault occurs to a side (b) of the in-use circuit 5, the multiplex modem unit 3' detects a step-out state due to the fault and confirms that the step-out state continues for about 2sec, sending a fault signal to a receiving switch control circuit 9 and then to a transmitting switch control circuit 7. Consequently, the receiving switch control circuit 9 changes a switch SW2' over to a dotted-line side. The transmitting switch control circuit 7, on the other hand, detects the step-out state of the opposite time-division multiplex device to open the switch SW5 of the in-use circuit 5 which is switched to a stand-by circuit for an enough time to operate the changeover switch of a receiving circuit. Consequently, a multiplex modem unit 4' detects the step-out state and sends a fault signal to a receiving switch control circuit 10 firstly and a transmitting switch control circuit 8 secondarily. |
