Telephone system ring period detector

摘要

An improved ring detector circuit is provided to discriminate between ring signals and low frequency dial signals. The circuit times the interval between pulses generated each time the incoming waveform exceeds a threshold and, if the interval is greater than 50 ms disables a ring detect circuit which is set by a pulse train, the interval between adjacent pulses of which is less than 50 ms. Pulses having a duration of less than 5 ms are eliminated to insure that chatter and sliver are not misconstrued as a ring signal.