Sync detection circuit

Details Sync detection circuit Sync detection circuit

1987-07-17

1989-03-21

Shepperd, John W.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358158, H04N 508, H04N 505

Patent

active

048148784

ABSTRACT:
A sync detection circuit detects a standard signal which is a signal having V-sync signals with a predetermined repetition period, a non-standard signal which is a signal having V-sync signals with the repetition period other than the predetermined repetition period, and a signal absent condition which occurs when the broadcasting is finished. The sync detection circuit includes a V-sync separator for separating V-sync signals, a counter for counting the predetermined repetition period in relation to each of the V-sync signals and for producing a count-up signal upon counting the predetermined repetition period, and a phase comparator for comparing the phase of the count-up signal with the phase of a V-sync signal and for producing a first level signal, representing the receipt of the standard signal, when the compared signals have the same phase, and a second level signal, representing the receipt of the nonstandard signal, when the compared signals have the different phase. The counter also counts a predetermined time period, which is greater than the predetermined repetition period, in relation to the V-sync signal and for producing a time-up signal upon counting the predetermined time period, and a condition detector for detecting the signal absent condition when no V-sync signal appears before the time-up signal is produced.

REFERENCES:
patent: 3609221 (1971-09-01), Langer
patent: 3878336 (1975-04-01), Balaban
patent: 4025951 (1977-05-01), Eckenbrecht
patent: 4231064 (1980-10-01), Uchida
patent: 4298890 (1981-11-01), Lai et al.
patent: 4387397 (1983-06-01), Dietz
patent: 4467359 (1984-08-01), Hosoya
'85 Semiconductor Handbook, Sanyo Electric Co., Ltd., pp. 1000-1002, 1344, 86 and 87.

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