30 September 1988
Horizontal sync pulses
a. At the bottom of the scene, when 262.5 horizontal lines have been
scanned, it is time for the beam to return to the top of the scene. The
start of vertical retrace is signaled by the vertical sync pulse that
differs in width from horizontal sync pluses (fig 1-4). Since the vertical
retrace takes much longer than the horizontal retrace, a longer vertical
synchronizing interval is used.
Relationship of vertical and horizontal sync pulses
b. During the time when horizontal and vertical retrace are taking
place, the electron beams in the camera and home television are cut off.
This time period is called blanking. Blanking means that nothing is written
on the television receiver screen.
c. During horizontal blanking, "sync burst" takes place (fig 1-5).
Also during the vertical blanking time, vertical sync, vertical equalizing
pulses, and vertical serrations occur. The equalizing pulses are inserted
to cause the video fields to begin at the proper points to achieve
The vertical serrations keep the television receiver's
horizontal sync circuitry from drifting off frequency during the time when