These are different synchronization methods used between cameras.Genlock is the best method for full synchronization between two cameras used in precision applications such as broadcast studio cameras. It synchronizes horizontal, vertical, even/odd fields, color burst frequency and phase.Vertical sync is the simplest way to synchronize two cameras. By using the vertical drive frequency, it ensures that video can be displayed from multiple sources on the same monitor using older switchers or quad splitters. The vertical drive signal typically consists of pulses with a repetition rate of 20/16.7 ms (50/60 Hz) and a pulse width of 1 to 3 ms.Composite color video sync represents video and color burst signals, meaning the camera can synchronize with an external composite color video signal.

However, despite being called composite color video sync, in practice only horizontal and vertical synchronization are performed, with no color burst synchronization.External sync is very similar to composite color video sync. One camera can synchronize to the video signal of another camera. An external sync camera uses an input composite color video signal, extracting horizontal and vertical sync signals for synchronization.

Most cameras support vertical drive sync or composite color video sync / external sync. However, since surveillance cameras never require line lock, nearly all CCTV cameras do not feature full genlock capability.DC line lock is an older technology that uses 50/60 Hz DC power line current to synchronize cameras. It was widely used in North America because 24V DC power is commonly available in most building fire alarm systems.Older switchers and split systems had no digital memory, so synchronization between cameras was essential to maintain stable images. DC line lock synchronizes cameras to the 50/60 Hz AC line. Since there is no constraint on the timing relationship between color channels and horizontal/vertical signals, poor color transitions (color phase shifting) will occur. For this reason, all users of AC line lock inevitably experience degraded color reproduction.

Fortunately, modern splitters, 16-channel multiplexers and digital video recorders include internal memory to overcome this problem and no longer require synchronization signals. As a result, AC line lock will likely become obsolete in a few years