Method and apparatus for monitoring the on/off-hook status of a

Details Method and apparatus for monitoring the on/off-hook status of a Method and apparatus for monitoring the on/off-hook status of a

1977-05-27

1978-08-29

Claffy, Kathleen H.

179 18HB, H04M 304

Patent

active

041105699

ABSTRACT:
In an extension line circuit, an off-hook condition is detected during ringing by superimposing in each ringing cycle the values of the line current existing at two sampling instants exactly one-half cycle apart, and testing whether the sum (or mean value) exceeds a given threshold. When DC current starts flowing due to the set going off-hook, the mean value of the two values will pass a threshold.
Sample pulses for the sampling instants can be derived in common for all line circuits from positive-going zero crossings of the ringing supply signal.

REFERENCES:
patent: 3746798 (1973-07-01), Thomas
patent: 3808378 (1974-04-01), Hernandez

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