When selecting a specific input source that can be processed by only a second voice-data processing unit instead of an input source currently being processed by a first voice-data processing unit, a voice-data processing circuit selects and delivers an input source selected by a second analog switch to the first voice-data processing unit by using a first analog switch. Then, after the first and second voice-data processing units simultaneously process the identical input source other than the specific input source over a certain time period, the second analog switch selects and delivers the specific input source to the second voice-data processing unit and a first switch selects an output of the second voice-data processing unit and outputs a voice of the specific input source as an analog audio output.