INTERLINE SPACING ADJUSTMENT CIRCUIT IN A SCANNING CRT VISUAL DISPLAY SYSTEM

摘要

AbstractA scanning CRT visual display system 10 is providedin which the operation of the CRT controller 21 whichprovides video blanking pulses and horizontal andvertical sync pulses (at B, 25 and 26) for controllingthe CRT display is temporarily halted when a larger thannormal vertical spacing between horizontal scan lines isdesired. During the time that the operation of the CRTcontroller is halted, which is accomplished by theselective blocking of clock timing pulses (at 33) to thecontroller 21, an auxiliary synchronous counter circuit62 effectively counts the clock timing pulses andprovides a substitute horizontal sync pulse (at G) forthe CRT display such that during the implementation of alarger than normal vertical step for the scanning CRTdisplay system, horizontal sync pulses are alwaysprovided even though the operation of the CRT controlleris temporarily suspended during this time.