| 摘要 |
<p>An echo prevention circuit is configured in such a manner that in a telephone receiving part (11) of one communication device (1), second amplifiers (A2,A3) connected to respective speakers (SP1,SP2) are provided separately from an amplifier circuit (A1) and that a distributing circuit (12) is provided for distributing, to these second amplifiers, the magnitude of a telephone reception signal voltage, which has been supplied from a transmission system (18) and amplified by the amplifier, in an unbalanced manner at any time such that an output voltage of a microphone (MIC1) is minimum. This prevents echo effect from occurring between the telephone receiving and transmitting parts of each of two communication devices (1,2), so that the telephone receiving and transmitting parts can be located at the same place or close places and a stable two-way telephone communication can be realized.</p> |
