Subscriber line control apparatus to concurrently detect change

Details Subscriber line control apparatus to concurrently detect change Subscriber line control apparatus to concurrently detect change

1995-05-02

1996-11-19

Hofsass, Jeffery

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379377, 379383, 379384, H04M 322

Patent

active

055771149

ABSTRACT:
A subscriber line control device utilizes a scan input table and a last look table. The scan input table stores respective current line states of a plurality of analog subscriber lines. The last look table stores respective preceding line states of the plurality of analog subscriber lines and information for validating or invalidating a timer device. A valid timer device corresponds to when a monitoring process is required. The scan input table is compared with the last look table at every predetermined cycle. When they do not match, it is judged whether the line state has changed or if the timer device is validated. Based on the judging result, an analog subscriber line control is performed according to an instruction specified by a call processing unit. The analog subscriber control is any of a call origination monitor, a dial pulse monitor, and an on-hook and off-hook (HIT) monitor.

REFERENCES:
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patent: 4792969 (1988-12-01), Shibata et al.
patent: 5058111 (1991-10-01), Kihara et al.
"Scanning Schemes in Electronic Telephone Systems", Y. Jayachandra, Telephony, Nov. 20, 1978, pp. 40-41, 44.
"A Comparison of Scanning Systems: Control Loop vs. bus Interface", Y. Jayachandra, Telephony, Jan. 1, 1979, pp. 26-28, 32.

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