Scan control circuit for a video terminal display device using f

Details Scan control circuit for a video terminal display device using f Scan control circuit for a video terminal display device using f

1975-04-24

1976-09-28

Wilbur, Maynard R.

Electric lamp and discharge devices: systems

Cathode ray tube circuits

Cathode-ray deflections circuits

H01J 2970

Patent

active

039834514

ABSTRACT:
In a video terminal system wherein a number of characters are to be displayed on each forward horizontal scan, a scan control circuit is utilized to synchronize the displaying of characters with the scanning of the cathode ray tube. Both the scan control circuit and the displaying characters are tied to a timing chain. Since the displaying of characters occurs at a fixed predetermined time in the timing chain, the scan control circuit is required to control the movement of the scan such that the phase of the scan is regulated in time. The scan control circuit accomplishes synchronization by a self-regulating feedback circuit which controls the magnitude of the base drive to a power transistor. Since the storage time of a power transistor is proportional to the magnitude of the base drive current to the power transistor, a simplified circuit results which accurately places the characters at a fixed position. The self-regulating feedback circuit also assures that the power transistor is precisely driven regardless of its parameters.

REFERENCES:
patent: 2852717 (1958-09-01), McCurdy
patent: 3179842 (1965-04-01), Brooks
patent: 3435280 (1969-03-01), Havn
patent: 3748527 (1973-07-01), Pluck

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