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Similar Data CRT Display Times Between Modes Eliminates Need to Switch "S" Capacitor in Monitor

IP.com Disclosure Number: IPCOM000064401D
Original Publication Date: 1985-Jul-01
Included in the Prior Art Database: 2005-Feb-18

Publishing Venue

IBM

Related People

Authors:
Saenz, JA Svominen, H Yosim, P [+details]

Abstract

A technique is described whereby the need to change the "S" correction capacitor used in CRT displays is eliminated when the horizontal drive frequency must be changed to provide variable scan lines. In the use of CRTs as display monitors, the horizontal drive frequency is required to be changed, so as to enable the display to support variable scan lines, for example, 200 and 350 lines. Generally, this means that the horizontal data display time must change. In order to maintain a linear raster to support the different data display scan lines, a high voltage "S" capacitor is used to provide the required resonant frequency for the horizontal deflection yoke. The value of the "S" capacitor is chosen so as to cause the horizontal velocity of the beam scan to be the same at the edges of the screen data area as it is in the center.