| 摘要 |
A dual mode cellular radio communication apparatus includes an echo canceller which cancels echo signals caused by acoustic coupling between a hands-free microphone and a loudspeaker in both analog mode and digital modes. An analog-to-digital converter and digital-to-analog converter may be used both in an analog mode and in a digital mode. A second analog-to-digital converter and a second digital-to-analog converter may be selectively used in the analog or digital mode. The echo canceller may be rendered inoperative during hand-set operation. In addition, a bypass circuit may be provided between an input and an output of the echo canceller so that the echo canceller is bypassed.
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