| 摘要 |
The circuit detects receiving error of dual tone multi frequency signal of a paging system connected to a private branch exchange. The circuit comprises a microprocessor (10) for controlling the paging system, a dual tone multi frequency (DTMF) signal detector (20) for detecting paging number transmitted from the private branch exchange, and for sending the received signal to the microprocessor, a DTMF signal modulator (30) for raising the level of input DTMF signal to the high state of TTL level, and a comparator (40) for detecting receiving error by comparing data output enable signal of the DTMF signal detector (20) with output signal of the DTMF signal modulator (30).
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