| 摘要 |
PURPOSE:To make transmission of power failure information surely without a limit of frequency band with a simple constitution, by transmitting a modulated output of fixed transmission when a commercial power supply is in failure and discriminating it at the reception side as the power failure through the detection of a long pulse. CONSTITUTION:When a commercial power supply is in failure, a power failure detecting relay 15 is inoperative, contacts 15K1 and 15K2 are changed over, a power is supplied to a modulator 13 from a battery 16 in place of a power supply 14, and a mark or a space hold signal is inputted from a generating section 17 in place of the output of a modulator 12. Thus, the output of the modulator 13 is a fixed transmission. On the other hand, at the reception side, alternate transmission of mark and space in the reception frequency is fixed into either the mark or the space due to power failure. This is detected at a detecting circuit 25 and it is discriminated as the power failure when the detected signal is in opposite phase to a long pulse generated at the interruption of line. |
