| 摘要 |
PURPOSE:To prevent malfunction by sending out a micro-sinusoidal wave signal to a distribution board side when the power supply on the terminal side is at work so that no power switch from the distribution board to the terminal can then be interrupted. CONSTITUTION:Judging from the output voltage of a power switch 4 at a constant value or more, a micro-sinusoidal wave generation circuit 7 detects the power supply at work, generates a sinusoidal wave signal of minute power and overlaps that output with a power line 12. On the other hand, the sinusoidal wave signal overlapped with the power line 12 goes through the power line 12 and flows back to a power distribution board 1. A sinusoidal wave detection circuit 8 detects the sinusoidal wave signal which flew back there. It is sent out to a power supply working control circuit 9 and to an indication circuit 10 whether or not there is a sinusoidal wave signal. When the sinusoidal wave signal exists, the power supply working control circuit 9 controls the operation so as to be unable to turn off a power switch 3 or so as not to cause interruption even though the power switch 3 can be operated to turn off. Such malfunction as turns off the power supply to the distribution board 1 by mistake when the terminals are used can thereby be prevented. |
