Cameras come in all shapes and sizes. There are ones that are front facing and ones that are rear facing or mirror image view.
If you are planning to side mount them looking rearwards, make sure you purchase cameras that are mirror image or can be programmed for mirror image.
I purchased my cameras for the trailer from Active-Vison, link below.
Wholesale CCTV Security Video Cameras, Surveillance Systems, DVR, GeoVision Digital Video Recorders
The first time through this project I purchased the wrong facing cameras for the left and right side of my trailer. When the images were displayed on my monitor they were always in the wrong orientation to what my brain was accustomed to viewing. Just recently, I replaced those with upgraded Sony cameras that are programmable so I can now set them up with a mirror image.
I have four cameras for my trailer. One inside looking at the cargo. One in the rear that gives me about a 130 degree angle view of the rear. One on each side of the trailer showing me about 1.5 lanes in both directions.
So I can watch traffic on each side of my trailer, then when passing, once I see the front of the vehicle in my rear-view camera, I know that it is safe to pull over to the right lane. can also watch for vehicles approaching from both sides of the trailer.
Next, you need a DVR with a hard drive. They come in various sizes. I chose the eight camera size and bought a 2 TB hard-drive. I am now using 6 of the 8 positions available.
You will also need a monitor. I purchased one from Amazon which is called IView. It's 15 inch and mounted on a flip down TV mount (purchased from eBay) that is secured to the bottom of the overhead cabinet above and in front of my driver's seat. When in position, it does not block my vision for driving.
I am now working on removing the OEM mirrors from the coach and installing the Ramco upgraded three-head mirrors with In-Vue cameras built-in to the lower mirror. That will give me complete rear side views for both sides of my coach. They will be active all the time, not just when the turn signals are active which is the way that the OEM Factory systems work.
Everything is powered by 12 VDC, cameras, DVR, monitor, etc.
I can take some photos later and post them if needed.
Dr4Film ----- Richard