| 摘要 |
PURPOSE:To ensure a calling action, etc., as prescribed even through a handset is kept off with a telephone containing a calling handset, by detecting surely a howler signal and cutting off electrically a telephone circuit. CONSTITUTION:A howler signal SH is delivered from an exchange to produce alarm tones from a handset 4 in case no on-hook signal is received from a telephone 9 for a prescribed period of time after an on-hook signal is received from the remote side of call and the talking is through. A level detecting circuit 13 receives the signal SH at a non-inverted into terminal of an arithmetic amplifying circuit 14. A microcomputer 8 delivers control signals SC4, SC2 and SC3 to an output circuit 25 and switch circuits 10 and 11 respectively after a detection signal SD is led to logic 'H'. The circuit 25 turns on and off an alarm lamp 26 in response to the signal SC4 and at the same time actuates a buzzer to inform users that the handset 4 is kept out of its prescribed position.
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