Low-frequency alternating current signal detector, in particular for central office line interface circuits
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United States of America Patent
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Jun 8, 1993
Grant Date -
N/A
app pub date -
Jun 19, 1990
filing date -
Jun 19, 1989
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A low-frequency alternating current signal detector for recognizing tone signals in a central office line interface circuit connecting a private telephone installation to an analog telephone network subscriber line. The low-frequency alternating current signal detector includes an amplifier (1) connected to the input of a bandpass filter (2) and to the input of a first rectifier-filter (3), a second rectifier-filter (4) and a threshold presence detector (5) connected to the output of the bandpass filter (2). The output of the threshold presence detector (5) selectively enables comparison by a comparator (6) of the bandpass filter input and output signals and signalling of the presence of an alternating current signal.
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