| 摘要 |
PURPOSE:To prevent an abnormality in the control after re-application of power by switching the connecting state of a telephone set for use with power failure to a trunk line during the power failure, storing this information, checking the storage information in response to the power application after the power failure and correcting the data of connecting state. CONSTITUTION:A control circuit CC1 comprising a resistor R15, a transistor Q13 and a capacitor C11 charged by a DC power supply +19V during power application of a commercial power supply AC is provided corresponding to a changeover switch Kp. When the switch Kp is operated and turned on in response to the power failure of the commercial power supply AC, an electric charge stored in the capacitor C11 is given to winding P, S of latching relays XC1, XC2 and the latching relay XC1 is operative forcibly. The operation of the switch Kp is discriminated during the power failure by the check of a control section CNT in response to the power application of the commercial power supply AC, data representing the state of the latching relays XC1, XC2 stored in a variable memory RAM before the power failure are corrected according to the present state and the control without any error is restarted. |
