| 摘要 |
The circuit processes receiving from the trunk of the private the DTMF digits branch exchange effectively by comparing the intially input DTMF signal to next incoming data. The circuit also processes the special key so that services for the subscriber is improved. The circuit comprises a DTMF receiver (DTMF1-n) converting the inptu DTMF 4 bit binary data to the channel unit, D flip-flops (CO1-n) comparing the present outputs of the DTMF receivers to the former data and providing the compared value to the corresponding channel, a port (10) reading the outputs of the D flip-flops periodically, a ROM (20) storing the program for DTMF signal process and system control, a RAM (30) storing the former and next DTMF data temporarily and a CPU (40).
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