RING SIGNAL DETECTION CIRCUIT

摘要

The circuit for detecting the ring signal provided from the switching system comprises: a rectifier (16), which is connected to the office line terminal through the capacitor and the resistor, outputting the office line signal; a zener diode (18) and a capacitor (20) clipping and smoothing the voltage; a ringer circuit (22) oscillating a fixed period of ringer tone; a speaker (24) connected to the output terminal of the ringer circuit; a circuit (26) for amplifying and outputting the ring tone regenerated from the speaker; a low pass filter (28) for waveform shaping the output of the circuit (26); a comparator (30) outputting ther ring detecting signal by comparing the output of the low pass filter with the standard voltage; a MPU (36) executing the automatic responsing mode.