| 摘要 |
PURPOSE:To use the titled telephone set by switching only a receiving voice from a loudspeaker monitor to a receiving call using an earphone in accordance with necessity at the time of a hand-free call, by providing a loudspeaker/ earphone changeover switch. CONSTITUTION:In case when an output voice level from a loudspeaker 7 is low, or a voice cannot be heard clearly due to noises of the periphery, etc., or in case when it is desired to set only a receiving voice to a privacy telephone, a loudspeaker/earphone changeover switch 6 is turned on, and a receiving sound signal is switched to an earphone 8. On the other hand, it is amplified by a microphone amplifying circuit 11, and thereafter, a level of a transmitting sound signal which has been rectified by a transmitting sound signal rectifying circuit 12 is compared with the receiving voice level by a voice level comparing circuit 3. As a result, in case when the transmitting voice level is higher than the receiving voice level, the transmitting voice connecting circuit 13 connects the microphone amplifying circuit 11 and a terminal 9, and the transmitting sound signal is sent out to a trunk line or a PBX line.
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