| 摘要 |
PURPOSE:To obtain an LSI-implemented signal detecting circuit which operates stably by preventing erroneous detection due to the noise and momentary break of a received signal, by providing a momentary-break detecting circuit to a circuit which discriminates the frequency digitally by binary-coding the received signal. CONSTITUTION:After received signal 1 is amplified, it is applied to BPF7 to eliminate its unnecessary noise and binary-coded received pulses 9 are outputted from comparator 8. Those pulses 9 are counted by N counter 10 up to N and also applied to momentary-break detecting circuit 23 to detect the momentary break of signal 1, and its output is applied to reset circuit 16. Main counter 11 counts clock 15 and N detecting circuit 17 outputs -N until the count value of counter 10 reaches N and then outputs N when it reached N. Then, while M counter 12 is controlled by N and -N, comparators 19a-19n are operated in every cycle to discriminate the reception frequency by a preset frequency, and (m) counters 13a-13n are driven to set correct signals of (m) cycles or more in detection storages 14a-14n during the M-cycle period. |
