| 摘要 |
<p>A system for automatically adjusting the level of a telephone instrument microphone input signal in response to the level of the telephone instrument sidetone signal. The system may provide a test signal to the handset microphone input and receive the sidetone signal that corresponds to the test signal from the handset speaker output. A signal processor may then measure the amount of distortion present in the sidetone. If the amount of distortion is below a predetermined threshold, the level of the test signal is increased by a predetermined increment by adjusting an attenuation or amplification factor, and the amount of distortion in the sidetone is again measured. These steps are repeated until the measured distortion exceeds the threshold. The level of the test signal is then decreased by a predetermined amount. The final test signal thus has a level that maximizes the microphone input signal level with an acceptable minimum of distortion. The test signal is then automatically disconnected and a signal produced by an external device, such as a modem, is automatically connected. The selected attenuation factor is thus applied to the signal produced by the external device.</p> |
