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On Fri, 17 Jul 2020 21:02:42 -0400, Clare Snyder
wrote:


I have a question maybe one of you fine folks would have an answer
for.
If I have one video monitor and several video cameras - regular hard
wired composite video - can I connect say, 3 cameras in parallel and
switch power between the three cameras to scan from one camera to the
next in sequence? I tried it with 2 backup cameras and no magic smoke
came out and they seemed to work just fine (for the couple of minutes
I had them connected). I even tried powering both at the same time and
the monitor just lost the signal. When I disconnected one, the other
came back up on the screen immediately. This would tend to indicate
the cameras have tristate outputs? Or at least open collector - when
not powered the output is disconnected???

I think you answered your own question for the ones you have tried.
Whether you can make a blanket statement is still an open question.
They do make multiplexors and you might be able to get another card
for your DVR to add more cameras. Mine is set up for 8 but I am a card
and a plate with more connectors away from 16.

In fact even the most basic security systems do it even better,
show all the cameras at once on a decent sized screen and
allow you to view just one at the time. Dirt cheap to buy.