The aim in video applications is to ensure the coincidence of signals in time at a combining or switching point.
Where two or more video signals are combined or being switched between, the horizontal and vertical timing of the picture sources should be coincident with each other.
If they are not, the picture will appear to jump when switching between the sources whilst the display device re-adjusts the horizontal and/or vertical scan to correctly reframe the image.
Generator locking can be used to synchronize as few as two isolated sources (e.g., a television camera and a videotape machine feeding a vision mixer (production switcher)), or in a wider facility where all the video sources are locked to a single synchronizing pulse generator (e.g., a fast-paced sporting event featuring multiple cameras and recording devices).
In broadcast systems, an analog generator-lock signal usually consists of vertical and horizontal synchronizing pulses together with chrominance phase reference in the form of colorburst.