Reversing camera systems can come in two basic wiring styles.
The first style uses an RCA cable to take the video from the camera to the monitor.
This method takes power for the camera from the reversing lights.
This is the simplest, and therefore cheapest, style of wiring.
The other option provides power for the reversing camera system using additional power extension cables.
This allows the reversing camera system always-on rear view. Waterproof four pin cables and connectors are used in this case.
The power to the camera is provided from the cable.
However, they are more expensive than the first option.