Interline spacing adjustment circuit in a scanning crt visual display system

Abstract From the Canadian patent

A scanning CRT visual display system 10 is provided in which the operation of the CRT controller 21 which provides video blanking pulses and horizontal and vertical sync pulses (at B, 25 and 26) for controlling the CRT display is temporarily halted when a larger than normal vertical spacing between horizontal scan lines is desired. During the time that the operation of the CRT controller is halted, which is accomplished by the selective blocking of clock timing pulses (at 33) to the controller 21, an auxiliary synchronous counter circuit 62 effectively counts the clock timing pulses and provides a substitute horizontal sync pulse (at G) for the CRT display such that during the …