Video Drive Pulses

Drive Pulses
Horizontal and vertical drive pulses are used for driving the camera and are never broadcast. These pulses trigger circuits in the camera called sawtooth waveform generators. The name “sawtooth waveform” refers to the shape of its signal, which looks like the serrations on the edge of a wood saw (Figure 4.2). Both the horizontal and vertical circuits are driven by the same sawtooth waveform.

In horizontal deflection circuits, the long slope on the sawtooth waveform drives the scanning electron beam horizontally across the target face of the pickup tube. In vertical deflection circuits, the long slope moves the beam vertically from one scanning line to the next. In both

horizontal and vertical deflection circuits, the shorter and steeper slope of the sawtooth waveform causes the beam to retrace. In horizontal deflection circuits, the beam moves back to start scanning another line. In vertical deflection circuits, the beam moves back to begin scanning another field.

Blanking Pulses
Horizontal and vertical blanking pulses cause the electron beam in a video camera to go into blanking. In other words, they cause the electron beam to shut off during the retrace period at the end of each line and the retrace period at the end of each field. Blanking pulses, like horizontal and vertical drive pulses, are fed to cameras.
However, unlike drive pulses, the blanking pulses are broadcast as part of the overall video signal.