I'm installing two security type DVR's that each have a VGA output. I would like to use one monitor with an AB switch, and switch between the two VGA DVR outputs. Can I damage anything with such an arrangement? Thanks, Lenny
As long as the DVRs will always output a signal even if no monitor is attached, there should be no problems. VGA stuff is birectional, although not everything interrogates the monitor.
Even those rediculous beige steel boxes with the black knob would probably be ok for the resolutions coming out of a security system.
Only one way to find out!
As far as I know, no monitor can be damaged by yanking the input signal. So the "burp" while switching shouldn't be a problem.
The only way that I know of that a monitor can be damaged is if it's a multi-sync model, and it's driven at a scan rate above its highest spec'd rate. Other than that...
William Sommerwerck explained on 30/08/2013 :
I know this is OLD History but- The early text only green IBM PC monitors needed a sync pulse from the CPU or they would "self destruct" The monitor was powered from the CPU power switch so that it cold not be left on alone. Of course that is really long ago history. ^^
-- John G
That sounds more like legend. I had a couple of Ball Brother open frame small monitors that I used back then, for my OSI Superboard and then my Radio Shack Color Computer. They needed a horizontal sync signal to generate the horizontal ramp (and the very high voltage), but if there was no horizontal sync signal, nothing bad could happen.
Michael
It is not legend. I was very specific about which Monitor it was, text only green IBM PC monitors ie the 5151. I was in IBM Computer Support at the time. :-?
-- John G
Okay, that's more defining. I wasn't sure if this was something you saw, or something someone else said was true. A bit of information can be worse than none at all.
Michael
For convenience, it's hard to beat a KVM swtich. I had a 4-monitor KVM. Switch button on the front or hook up a keyboard and hot-key select. Oughta be a zillion of 'em at surplus outlets. The Two-port ones are a dime a dozen if you live in an area with garage sales.
Also maintains signal continuity so you don't get ghosting with long cables.
I once had an *old* tube TV-monitor (from a TV station control room).
I had it connected to a Sinclair ZX-81, which use the CPU for also generation the video signal.
The ZX-81 could be put in "Fast" mode, where it used all the CPU-time for computing instead of video generation, so the video was not proper synchronized.
This unsynchronized signal probably had a higher flyback frequency or something, causing the high voltage to go bananas, so sparks flew, which produced large bangs from inside the monitor.
When the monitor finally died, it got replaced with a B/W tv, where I cut a trace from the tuner and applied the video signal to the pcb.
This ZX-81 later got fitted into a rack, with a wirewrapped 64Kb expansion ram and 6 channel audio. Even later, the CPU lived on in a CP/M-plus system with a whopping 3/4 MB ram. But that's another story.
Leif
-- Husk kørelys bagpå, hvis din bilfabrikant har taget den idiotiske beslutning at undlade det.
No legend. That early monitor is the reason the original PC had the power outlet for a monitor on the PC's power supply. I saw more than one monitor that caught fire from lack of horizontal drive.
-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
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