| 摘要 |
PURPOSE:To prevent the leaving of the handset from off the hook, by providing the signal generation circuit provided at the handle of the handset, NOT circuit for the signal from the circuit and timer. CONSTITUTION:No signal is appeared at the output of the AND circuit 4 since the signal is produced from the OFF HOOK signal generation circuit 1 of the hook switch and the handle signal generation circuit 2. Accordingly, no alarm is made from the speaker 7. If the handset is left off the hook at the end of communication, since no signal is produced from the handle grip signal generation circuit 2, a signal is outputted from the NOT circuit 3, and output is made from the AND circuit 4 and it is inputted to the timer 5. After time T, the output of the timer 5 is at high level, alarm tone is produced from the speaker 7. |
