Method of and circuit arrangement for evaluating the output sign

Details Method of and circuit arrangement for evaluating the output sign Method of and circuit arrangement for evaluating the output sign

1986-12-17

1988-04-05

Ng, Jin F.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379377, H04M 322

Patent

active

047364122

ABSTRACT:
The flow of direct current and/or ringing alternating current in a telephone line subscriber loop is detected by means of current flow detectors. The output signals produced by the current flow detectors are applied to an evaluation circuit, the zero-crossings of the ringing alternating current being used to determine whether a ringing alternating current has been superimposed on the loop direct current.
In order to increase the reliability of the evaluation and to detect noise voltages coupled into the subscriber-loop, the durations of positive and negative half-waves of the loop current are measured and the evaluation is effected by comparing the sum and the ratios of the measured values relative to a presettable threshold.

REFERENCES:
patent: 4197435 (1980-04-01), Jackson et al.
patent: 4356355 (1982-10-01), Ferrieu
patent: 4524245 (1985-06-01), Littlefield
patent: 4540854 (1985-09-01), Beirne
patent: 4679229 (1987-07-01), Yamaguchi
patent: 4689816 (1987-08-01), Wood

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