What is "Genlock" on a camera?

Answer 1

Genlock is the sychronization of multiple video devices connected to the same switcher. A video monitor consists of several lines on the screen that make up the picture. When 2 cameras are not in sync, the image will "jump" as it switches from one camera to the other. Synchronization prevents this from happening because the signals from both cameras will not interfere with each other.

This form of syncronization comes through the genlock ports on the cameras and the switcher.