| 摘要 |
PURPOSE:To obtain excellent talking by adjusting the intensity of transmission or reception depending on the degree of howling by the transmission/reception of a duplicated signal so as to prevent the generation of unpleasant high frequency noise. CONSTITUTION:When a telephone system 1 of an automobile A and a telephone system 21 of an automobile B are connected, a prescribed level of pilot signal (f) is sent form a pilot signal output section 15 in the controller 4 of the system 1 and inputted to a microphone 2 from a speaker 3 via an amplifier 14 and sent from a transmission section 11. The transmission signal is inputted to a microphone 25 from a speaker 24 of the system 21 via a relay station X and inputted to a reception section 12 of the system 1 via a relay station X and the output is inputted again to the microphone 2 from the speaker 3. In this case, the output of the microphone 2 is inputted to a decision section 16 at the same time and the degree of howling is decided by the comparison with the signal (f) and when the degree is a prescribed value or over, the gain of an attenuator 13 and the amplifier 14 is lowered by the control section 17 to suppress the generation of howling.
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