| 摘要 |
PURPOSE:To easily enter a reception state in a high-noise atmosphere and to easily enter a transmission state in a low-noise atmosphere by dividing a reception loss circuit and a transmission loss circuit respectively, and combining those loss circuits properly when a noise level exceeds a preset transmission threshold level. CONSTITUTION:When a voice is inputted to a microphone 1 in a no-noise state, the 1st and the 2nd transmission loss circuits 14 and 15 are controlled to the large amounts of loss and the 1st and the 2nd reception loss circuits 15 and 16 are controlled to the large amounts of loss, so that the circuit enters a transmission state. Then, if there is a noise exceeding the transmission threshold level and the device is in the transmission state while the amount of loss of the 1st transmission loss circuit 14 is large and the amount of loss of the 1st reception loss circuit is large, a loss amount control circuit 17 increases the amount of loss of the 2nd transmission loss circuit 13 and decreases the amount of loss of the 2nd reception loss circuit 16. At this time, the gain of areception detecting circuit 10 is increased with the control signal of a speech switch control circuit 11. |
