Telephonic communications – Supervisory or control line signaling – Using line or loop condition detection
Patent
1997-12-09
1999-11-02
Isen, Forester W.
Telephonic communications
Supervisory or control line signaling
Using line or loop condition detection
379373, 379377, H04M 306
Patent
active
059784717
ABSTRACT:
A ringtrip detector comprises a reference counter for controlling a battery current generator, which shapes the ring signal, a zero pass detector for detecting zero passes in a voltage at a node, which is proportional to the telephone line current and two other counters. The zero passes of the voltage create a pulse at both the positive and the negative zero crossing of the zero pass detector. The reference counter is gated into a memory, when these pulses appear. The zero passing of the previous and the present ring cycle are stored in the memory. A counter decides the difference between the previous and the present ring cycles zero passes. If the zero pass difference between the present and previous ring cycles is greater than a fixed value, the output will indicate a "phase difference" and if it is less than the fixed value it will indicate "no phase difference". Another counter counts a predetermined number of successive ring cycles with "no phase difference" at the start of a ring burst signal, and after establishing the ring burst signal, another predetermined number of successive ring cycles with "phase difference" is counted to detect the ringtrip.
REFERENCES:
patent: 4110569 (1978-08-01), Schindler et al.
patent: 4132864 (1979-01-01), Feng
patent: 4304970 (1981-12-01), Fahey et al.
patent: 4477698 (1984-10-01), Szlam et al.
patent: 4540853 (1985-09-01), Albouy
patent: 4731828 (1988-03-01), Basehore
patent: 5402482 (1995-03-01), Minohara et al.
Isen Forester W.
Saint-Surin Jacques M.
Telefonaktiebolaget LM Ericsson
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