| 摘要 |
In the present invention, with respect to a transmission line to which a plurality of devices are connected, a check is performed to determine whether there is a failure in the operation of any of the devices due to a drop in the voltage of the transmission line, and power source voltage is switched in two stages. The following are connected to a control-signal transmission line: a parent station that transmits a control signal to a plurality of control-target devices; and a plurality of child stations that are respectively connected to the plurality of control-target devices. In the case of a first operation failure state, in a child station, in which the present value of the current or voltage of a control-target device is smaller than a first threshold value that is the value of the current or voltage necessary for turning a control-target device ON, a first operation failure signal is output, and if such present value is smaller than a second threshold value that is the value of the current or voltage necessary for maintaining the ON state, a second operation failure signal is output. Further, the child station outputs the power-source voltage obtained from the transmission line as a first voltage which is necessary for turning the control-target device ON, or as a second voltage the power consumption of which is less than the first voltage that is sufficient for maintaining the ON state, and which is higher than a return voltage. |
