| 摘要 |
<p>PURPOSE:To eliminate the need of volume adjustment of speaker reception by making the gain of an amplifying circuit different between on-hook and off-hook to change the volume in a car telephone set having the speaker reception function by which traffic information or the like can be heard even at the time of on-hook. CONSTITUTION:A resistance R3 is provided in the input part of reception voice, and a switch 1 which can shortcircuit both ends of the resistance R3 is provided, and the switch 1 is controlled by a control circuit 9. When a hook switch is turned on and a hook line is in the high level, the switch 1 is turned off and the resistance R3 is inserted to the input side of an amplifier 5, and therefore, the gain of the reception voice side is reduced. When the speaking state is set, the switch 1 is turned on and the resistance R3 is in the short-circuit state, and therefore, the reception voice is amplified with a sufficient gain. When the speaker reception state is set, the switch 1 is turned on and the resistance R3 is short-circuited, and traffic information is amplified with a sufficient gain.</p> |
