| 摘要 |
<p>A unique speakerphone for cellular telephones includes in the transmit audio path between microphone (112) and transmitter (118), a transmitter mute switch which disconnects the audio path to the transmitter from the microphone (112), and a transmit gain amplifier that is controlled to lower the feedback the microphone can pickup from the speaker (110). In the feedback path to the radiotelephone receiver (120) from the cellular base station (122) and the land line telephone system (124), the speakerphone includes the controlled amplifier (106) which is fed into the speaker mute gate, and the speaker (110) to close the feedback loop. Deemphasized audio is sampled by the A/D (102) on both the microphone-to-transmitter side of the loop and the receiver-to-speaker side of the loop. The microcomputer (104) is able to detect and eliminate howl, as well as determine whether howl exists, from the A/D sampling.</p> |
