| 摘要 |
A device for automatically identifying DTMF and FSK system is disclosed. A signal detector is provided for detecting signals on a telephone line. A DTMF and a FSK decoders are provided for decoding DTMF and FSK signals, respectively. A microprocessor is activated when the signal detector detects a signal on the telephone line for only activating the DTMF decoder to calculate frequency spectrum of the detected signal. When the calculated frequency spectrum conforms to DTMF frequency spectrum, it is determined that a DTMF system is in use. When the calculated frequency spectrum only has a frequency of about 1,200 Hz or 1,300 Hz, it is determined that a FSK system is in use, so as to deactivate the DTMF decoder and activate the FSK decoder.
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