| 摘要 |
PURPOSE:To reduce the cost of a monitoring device by folding a monitoring signal in a device provided with a circuit to be monitored and giving this signal to a next device. CONSTITUTION:The monitoring signal is given to one of plural spare circuits and folded in this spare circuit and given to another spare circuit, and it is discriminated whether the operation of plural spare circuits is normal or not by the monitoring signal passing all of plural spare circuits. For example, the monitoring signal from a first circuit 401 for low-order group lines to a second circuit 402 for low-order group lines, and hereafter, the monitoring signal is folded and given from the second circuit 402 for low-order group lines to a third circuit 403 for low-order group lines and from the third circuit 403 for low-order group lines to a fourth circuit 404 for low-order group lines similarly. The output signal of the fourth circuit 404 for low-order group lines is returned to the monitoring device, and it is discriminated in a monitoring signal reception circuit 412 whether the circuit operation is normal or not. Thus, spare circuits are inexpensively monitored with the simple constitution. |
