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Browse Prior Art Database

CRT Character Size Control

IP.com Disclosure Number: IPCOM000092559D
Original Publication Date: 1966-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Gundrum, RJ: AUTHOR

Abstract

The circuit provides selective control of the size of characters displayed on a digitally controlled CRT display.

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CRT Character Size Control

The circuit provides selective control of the size of characters displayed on a digitally controlled CRT display.

A binary-coded signal representative of the magnitude of the X direction deflection and a size signal are applied to a converter circuit. The latter provides an analog current corresponding to the magnitude of the deflection in the X direction. This current is supplied to buffer amplifier 2 which is connected to X deflection yoke 4. A similar converter and yoke are provided for the Y direction.

The deflection signals cause the beam to trace a linear segment of the character. A variable number of sequential segments is provided for each character. The digital value of the signal and the gain of amplifier 2 determine the amount of beam movement or size of the segment.

The size signal is passed unaltered to switch 6 which is closed whenever a large size character code is supplied and opened when a small size code is supplied. When the switch is closed, resistor R1 in the divider network R1R2R3 is shorted thus increasing the control voltage of emitter-follower amplifier 8 which increases the gain of amplifier 2. When the gain of amplifier 2 increases, the beam is deflected a greater amount thus increasing the character size. When switch 6 is open, the control voltage of amplifier 8 is reduced and therefore the gain of amplifier 2 is reduced correspondingly.

This arrangement provides one of two size characters in response to a si...