| 摘要 |
<p>TITLE MULTIFREQUENCY SIGNAL PARITY DETECTOR A parity checking circuit for use in multifrequency tone receivers is disclosed wherein associated receivers are made less susceptible to digit simulation when talking is present, by verifying that the same two tones are present for the entire parity timing period. The circuit includes two groups of form detectors, with one detector for each touch calling frequency. Timing of the tone present in each group for parity, determines the presence of a valid signal, by means of timing and latch circuitry included.</p> |
