| 摘要 |
<p>PURPOSE:To attain stable service even at the power failure by switching to a DC power supply automatically in accordance with a call signal when a call is originated from a calling telephone set under power failure. CONSTITUTION:At the power failure, a call signal from the calling telephone set is applied to a terminal 9 and detected by a level signal detector 10, a relay 12 is actuated and a contact 13 is switched to a boosting converter 14 side to hold the state of the relay 12 in a relay holding part 11. On the other hand, a power failure detecting part 15 detects the power failure simultaneously with the power failure, actuates a relay 16 and turns a contact 17, so that current of a battery supplies working voltage to a terminal 19 through a boosting converter 14. Consequently, a telephone transfer device operates normally. After completing talking, a circuit releasing signal is sent from the telephone transfer device to a control signal terminal 20, the holding part 11 is reset and the contact 13 is returned to the original state.</p> |
