| 摘要 |
PURPOSE:To enhance the convenience by making the operation required for talking with an operation section provided to a handset at the outside of a portable telephone set main body and able to input and output each signal such as an on-hook signal, an off-hook signal, a transmission voice signal and a reception voice signal. CONSTITUTION:A switch 1.3 is provided to a transmission side in a head set 1.1 and the switch is closed at transmission and reception to connect a microphone 1.2 to the circuit, then a voltage changes at a portable telephone set keyboard section 1.6. A voltage detection circuit 1.7 detects the voltage change and sends an off-hook signal transmission request to a hook signal transmission circuit 1.8. The hook signal transmission circuit 1.8 sends an off-hook signal to a CPU 1.9 of the portable telephone set keyboard section 1.6. Moreover, the circuit operation is inverted in the reception standby mode.
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