| 摘要 |
PURPOSE:To prevent a fault in advance by allowing a lock circuit operated through the reception of a signal of a detection circuit detecting the drop of a battery voltage to inhibit the automatic response operation even when a trigger input after the end of restoration is detected. CONSTITUTION:When a power voltage drops to a prescribed value or below, a current does not flows to a Zener diode ZD, a transistor Q2 is turned off, the level at an input terminal 6 is brought to an H level and a level of a terminal 4 is decreased to an L level. Thus, an input terminal 8 being a set terminal of an integrated circuit IC2-3 is decreased to the L level, a flip-flop comprising integrated circuits IC2-3 and IC2-4 is inverted and a level of a terminal -Q' is stored to the L level. Even if a telephone set rings with the next incoming, since the input terminal 9 of the integrated circuit IC1-3 is kept to the L level by the Q4' output of the integrated circuit IC2-4, the telephone set does not respond to the call. |
