DIAL SIGNAL RECEIVER

摘要

PURPOSE:To realize the application of a dial pulse even with intervention of a device that gives no permission of pass to the DC component, by counting the impulses caused by the dial pulse that passed through a device that passes only the AC component. CONSTITUTION:The impulse caused by a dial pulse is turned into a DC waveform through a rectifying/smoothing circuit A to be applied to a comparator A, a B-level storage circuit LM and a detecting circuit DET. The circuit DET delivers a pulse only when the first impulse arrives; and the circuit LM monitors the maximum level of a DC waveform in a period during which an output pulse exists and decides either level A or B for the input to then store it. Comparators CA and CB transmit the output pulse to a counting circuit CNT every time it decides the impulse based on the level stored in the circuit LM. The reference of comparison is set up with the first impulse to cope with different conditions of a transmission line. Timers TIMA and TIMB have the guarding function to the noise.