View Single Post
  #6   Report Post  
Old July 18th 20, 04:38 AM posted to
[email protected] is offline
external usenet poster
First recorded activity by DIYBanter: Jul 2007
Posts: 12,471
Default security cameras - question

On Fri, 17 Jul 2020 22:19:38 -0400, Clare Snyder

On Fri, 17 Jul 2020 20:58:04 -0500, Snag wrote:

On 7/17/2020 8:19 PM, wrote:
On Fri, 17 Jul 2020 21:02:42 -0400, Clare Snyder

I have a question maybe one of you fine folks would have an answer
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.

Before I moved up here I had a computer set up with a card from Q-See
that would run 4 cams . I could either pull up one cam full screen or
all 4 of them at once on a quartered screen . You didn't say what kind
of box you have running them ... most DVR setups have multiple inputs
with the same features as the card I was using . I could also set that
comp up with a static intranet IP and use any other comp in the house to
watch the cameras . I don't remember how much control I had over things
when viewing from a remote .

It's a simple monitor - actually a stereo head unit in a vehicle. It
is set up for a backup camera. I want to have backup and sife view
cameras - selectable (backup comes on in reverse, left with left
signal,right with right signal - and backup over-rides signals. Sinnce
askingthe question I found another guy on the internet fif basically
the same thing - but front and rear cameras. Multiple NTSC Composite
cameras can be connected together without harming any of them - and as
long as only one is powered at a time they will not "walk over" each
other. 2 on at a time produces an ambiguous signal - so apparently I
SHOULF be able to do what I was thinking - - - -

I suppose you could use relays, shielded to isolate the inputs when
the camera wasn't active if you were really worried about it. A single
12v n/o reed relay in a metal can with coax connectors on each end
should work.