Normally, the backup camera turns on when the vehicle gear is in reverse.
That is due to the backup cameras are powered by the reverse backup lights and the monitor is triggered to view the backup camera when the gear is in reverse.
However, consider a situation where a vehicle is pulling a trailer and the driver wants to make sure that the trailer is hitched as he starts to drive away.
How can this problem be solved?
One way is to add a second camera for such need.
Another way is to add the switch to turn the backup camera on demand.
Most of the BOYO cameras include an extension with the red wire at the base of the RCA video jack which plugs into the monitor. At the other end is also has the same configuration and the red wire is continuous from one end to the other end.
Instead of powering the camera from the reverse backup light, use this red wire, if one powers the camera.
Wire the backup camera as shown below and install the switch at the driver's reach.
The driver can turn on and view the rear camera whenever in need.