Detector circuit for communication lines

Details Detector circuit for communication lines Detector circuit for communication lines

1981-09-30

1983-12-27

Brown, Thomas W.

H04M 322

Patent

active

044232926

ABSTRACT:
A detector circuit for detecting the on-hook and off-hook states of a communication line includes current and voltage sensors for generating two reference signals. One signal represents the current flowing in the line; the other represents the voltage on the line. A comparator circuit compares these two references to generate an output signal representative of the on-hook state when the magnitude of one of the references is greater than the other. When the magnitude of the one reference signal is less than the other, the comparator circuit generates another output signal representative of the off-hook state of the line. In addition, when the line is electrically isolated from ground, the two comparator output signals may drive an opto-isolator to generate two corresponding output signals electrically isolated from the comparator output signals.

REFERENCES:
patent: 4027235 (1977-05-01), Macrander et al.
patent: 4056691 (1977-11-01), Freimanis et al.
patent: 4099032 (1978-07-01), Roge et al.
patent: 4110565 (1978-08-01), Gaetano
patent: 4282407 (1981-08-01), Stiefel
patent: 4289933 (1981-09-01), Henry
patent: 4310725 (1982-01-01), Mehaffey
patent: 4349703 (1982-09-01), Chea, Jr.

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