[rescue] Re: Video Switch?

[Tim H.]

On Fri, 11 Oct 2002 00:01:25 -0400
Eric Webb <ttlchaos at randomc.com> wrote:

> I thought a lot of the benefit of using a powered KVM for this purpose
> were the proc amps inside.  Using any kind of switching (whether
> manual or electronic) typically implies twice the cabling as normal
> and I thought video was very sensitive to that (ie, length of wire).
> 
> You're very right about impedance mismatching, going from wire to pin
> to pin back to wire again, etc, etc...
> 
> But then, my electronics background isn't well-schooled.
> 
> 
> -E.

Length of cable is no where near as critical as quality of cable, I have
seen 50 foot VGA runs that have a very slight drop in brightness, and no
visible degradation in picture.  I have a Sun 13W3 20 foot monitor
cable.  The problem with the A/B type VGA switches that I have seen is
that they are inexpensive.  This means no shielding, noisy switches,
circuit board traces laid out with no thought for low RF analog signals,
junky connectors.  

Any one of those things can hurt you, all of them make decent
resolution/refresh really ugly.  If you look at places like Black Box
you can find good A/B switches, but then you are paying as much as an
inexpensive KVM anyway.  By the way, the same problems affect cheap KVMs
as well.  

The truth is, the keyboard/mouse circuitry in a KVM is probably
significantly less expensive than the hardware to switch the video
signal, and the connectors to hook to it, so it makes sense that a good
quality A/B switch costs just about as much as a similar quality KVM.

Tim