The picture and sync must be combined

Analog Sync Generator Signals (2)

Combining Sync with Video

Take a moment and think about how the video system has been described here. The CCDs in the cameras are converting the light images into electrical signals, but the drive, blanking, and sync pulses that tell those CCDs to scan a line, turn down, retrace, turn back up, scan another line, start a new field, and so on are coming from outside the camera. Yet coming out of the camera, the video and sync information are combined. This is called composite video; video information without the sync information is called noncomposite video. So when you look at the waveform monitor, you're looking at composite video.

In a broadcast-quality system, video is always 1.0 V (140 IRE units) peak to peak (from the bottom of the sync pulse to the top of the white peaks) across a 75-H impedance. By looking at the figure to the right, you can see that the video portion is 0.7 V and the sync portion is 0.3 V (these figures are rounded off; the video portion is actually 0.714 V, and the sync is 0.286 V), adding up to 1.0 V. The entire video signal is less powerful than the energy from a flashlight battery.

Components of composite video.