Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1979-05-25
1980-10-14
Murray, Richard
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
H04N 504
Patent
active
042284619
ABSTRACT:
A two-mode digital vertical synchronization system is described for controlling the phase synchronization of vertical scan in a television receiver. In one mode, the system searches for incoming vertical sync pulses which occur during a wide sync "window". Sync pulses received during that window are utilized to initiate vertical scan. When the received sync pulses are in time-coincidence with an internal control signal generated at a standard line/frame rate, the system switches to a narrow window mode of operation. Vertical sync pulses received during a narrow sync window continue to initiate vertical scan. When a lack of time-coincidence between received vertical sync pulses and the control signal occurs for a predetermined interval, the system reverts to its wide window mode. Preferably, the locally generated control signal has a time duration sufficient to permit detection of coincidence between itself and a typical non-standard vertical sync pulse to hold the system in the narrow window mode, thus preventing oscillation between the narrow and wide window modes.
REFERENCES:
patent: 3899635 (1975-08-01), Steckler et al.
Coult John H.
Murray Richard
Zenith Radio Corporation
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