| 摘要 |
PROBLEM TO BE SOLVED: To provide a communication apparatus comprising a semiconductor DAA that accurately detects a calling signal at a low cost. SOLUTION: In a communication apparatus 1, positive and negative voltage variations of a channel signal are binarized and binary signals are output by a binary data switching part 21. The positive and negative binary signals are switched and output under control by a CPU 24 corresponding to the operation of an operating part, the edge interval of the binary signals output from the binary data switching part 21 is measured to detect the frequency of the channel signal by a frequency detecting part 22 and on the basis of the frequency of the channel signal detected by the frequency detecting part 22, the CPU 24 detects a calling signal. Consequently, even a pulsed calling signal or a calling signal having a waveform that is different in rising and falling, can be accurately detected at a low cost without providing a calling signal detecting circuit using a photoelectric element. COPYRIGHT: (C)2005,JPO&NCIPI
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