The camera can transmit images synchronously. When did it start?

Vertical synchronization, color video composite signal synchronization, external synchronization, DC line locking and complete synchronization are different synchronization methods between cameras.

Integrated locking is the best way to completely synchronize two cameras in precision applications (such as radio studios). It will synchronize: horizontal, vertical, even/odd areas, color trigger frequency and phase.

Vertical synchronization is the easiest way to synchronize two cameras. By driving the frequency vertically, you can display video on the same monitor using the old-fashioned switching cycle or quadrant. The vertical driving signal usually consists of pulses with a repetition frequency of 20/ 16.7 milliseconds (50/60 Hz) and a pulse width of 1~3 milliseconds.

The color video composite signal represents video and color trigger signal, which means that the camera can be synchronized with the external composite color video signal. However, although it is called color video composite signal synchronization, it actually only performs horizontal synchronization and vertical synchronization, and there is no color trigger synchronization.

External synchronization is very similar to color video composite signal synchronization. One camera can synchronize with the video signal of another camera, and the external synchronization camera can extract the horizontal and vertical synchronization signals by using the input color video composite signal for synchronization.

DC line locking is an ancient technology, which uses DC 50/60 Hz power line current to synchronize the camera. Because DC 24 volt power supply is widely used in fire alarm systems of most buildings, it is very easy to obtain. Because the old switcher and segmentation system have no digital storage function, it is necessary to synchronize the cameras in order to maintain a stable image. DC line locking means that the camera is synchronized with AC 50/60 Hz. The time correlation between color channels and unconstrained horizontal/vertical signals will lead to poor color conversion (color phase design), so all users who use AC line locking will inevitably lose good color conversion. Fortunately, the existing splitters, 16-channel complex processors and hard disk video recorders all have internal memories to overcome this problem, and synchronization signals are no longer needed, so AC line locking may be eliminated within a few years.