Sensor alternating signals low frequency, in particular, for convenience central office termination equipment

摘要

Detector of alternating signals low frequency, in particular for the recognition of signals of the tone in a colic of a private telephone installation. / p & & p & the detector comprises an amplifier 1 is connected to the input of a band pass filter - 2 and, on the other hand, at the input of a first rectifier - filtering cell 3, a second rectifier - filtering cell 4 and a threshold presence detector 5 connected to the output of the band pass filter - 2. The output of the detector 5 permits or not the comparison with a comparator 6 between the input and output signals of the filter and a signalling the presence of the alternating signal.