Telephone call signal processing arrangement - uses call tone recognition circuit which either accepts or rejects a clock signal depending on position in signal band.

摘要

The circuit arrangement for processing telephone - voice frequency call signals accepts AC signals within a permissible frequency range. AC signals outside this range are not regarded as voice frequency call signals. A call tone recognition circuit either accepts or rejects a clock signal depending on whether it lies within the calling tone - clock frequency band or not. For frequencies (fw) of the AC signals up to a threshold frequency (fwg), the clock frequency increases monotonically with the frequency of the ac signal, but for frequencies above the threshold, the clock frequency is restricted to a frequency zone (ftm, ftl) above the call tone-clock frequency band (bft). ADVANTAGE - Sufficient signal content provided for reliable evaluation and recognition of call signals.