| 摘要 |
PURPOSE:To restore the sound volume automatically to a reference reception sound volume at the end of talking even when the sound volume is changed during talking by providing a means for storing changeover information of a changeover switch of reception sound volume and a hook switch and using an output signal of the storage means to allow a reception sound volume control circuit to apply sound volume control. CONSTITUTION:When a talker depresses a non-lock type sound volume changeover switch 10, a flip-flop circuit 13 is turned on to drive a reception sound volume control circuit 14 and sufficient talking is attained with a sufficient reception sound volume. The flip-flop circuit 13 is turned off by a hook switch 15 at the end of talking to restore the reception sound volume control circuit 14 to the original state.
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