LOW FREQUENCY ALTERNATIVE SIGNAL DETECTOR, IN PARTICULAR FOR TELEPHONE JETTER

摘要

P Low-frequency AC signal detector, especially for the recognition of tone signals in an analog trunk trunk of a private telephone system. / P P The detector has an amplifier 1 connected to an input part of a bandpass filter 2 and secondly at the input of a first filter-rectifying cell 3, a second filter-recovery cell 4 and a threshold presence detector 5 connected at the output of the bandpass filter 2. The output of the detector 5 allows or not the comparison by a comparator 6 between the input and output signals of the filter and a signaling of the presence of the expected alternative signal. / p