[mdlug] Looking for a good industrial KVM

[David McMillan]

     I'm working on an industrial control system that just seems to be 
having a goshawful time with KVMs.  We've gone through two expensive, 
high-end units already, and I'm looking for some advice.

     The control system in question is a PC using a remotely located 
industrial touchscreen-keyboard combo unit for a Human-Machine 
Interface.  The HMI has a VGA cable and a USB cable, and to the PC looks 
like a normal VGA monitor and USB keyboard/mouse, although the 
touchscreen does require an additional driver to be installed.

     My big problem is the VGA.  We just keep having serious problems 
getting the display to work reliably.  The screen tends to be fuzzy, 
have "wipe" effects where certain screen items seem to "smear" 
horizontally, and we've had issues with the color channels losing sync 
(so that an icon would look like three separate red/green/blue copies of 
itself stacked not-quite-perfectly atop each other), and just today the 
KVM that was working halfway decent last week has suddenly lost its red 
channel entirely.  We've confirmed it's the KVM by plugging a test 
monitor directly into the PC's VGA socket, and at that point 
everything's fine.

     The primary constraint I'm dealing with is cable length.  The 
complete cable run is a little over 50 meters.  The KVMs we bought were 
*supposed* to be spec'd for that distance, with a "host" and "slave" 
module linked by a straight Cat5 cable (no TCP/IP involved, no hubs or 
switches, just some sort of proprietary direct protocol) and breaking 
out the VGA and USB cables on each end.  It *looked* like such a simple, 
COTS-solved issue when we started....
     Adding a remote PC at the far end to act as a VNC or RD client 
isn't in the cards.  I just really need a way to get a plain-vanilla KVM 
to work cleanly and reliably over this kind of distance.