| 摘要 |
PURPOSE:To enable to use a button telephone set normally used when the power supply is ON, for incoming response use at power failure, by connecting a power failure monitor relay to the power supply circuit. CONSTITUTION:If power is failed and the output of a power supply circuit 2 is interrupted, a power failure monitor relay 3 is restored and the main trunk is connected directly to a telephone set 3 without a channel switch matrix 9. Thus, the incoming call on the main trunk is displayed on a telephone set 13 with an incoming call detector 12, and when the operator hooks up a handset, the telephone set 13 can be connected to the main trunk. |
