| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of a noise from a speaker by judging a break of a PCM sound signal from a source equipment without a one shot circuit and precisely judging a listening mode when the PCM sound signal is inputted after judging as the break. SOLUTION: The pulse of the PCM sound signal is inputted to an edge interruption port of a control microcomputer 14, and the interruption is generated at a pulse rise time. When the next interruption is not generated for a first prescribed time from the time when the interruption is generated, the PCM sound signal is broken is judged, and further, a second prescribed time is measured. Then, when the PCM sound signal is not inputted for the second prescribed time, the mute is operated.
|
