[geeks] Odd KVM question

[Fred]

Hi all

I am familiar with KVM's (and use them) in the sense they usually share
keyboards, displays, and sometimes mice.  Can be USB or PS/2 (and perhaps
others on the "newer" KVM's I'm seeing.  They usually gather their power
via USB, PS/2 or sometimes from the wall.

I have an oddball situation that I don't know how to solve.  In an effort
to save space, I have two text terminals (a VT525 and a CLI 5250 terminal)
stacked on top of one another.   One LCD on top that likes the refresh
rates of both terminals enough to be readable.

I'd like to share just the LCD between the two terminals without having to
swap the actual VGA cable.

I've always been taught/told that those old school beige A/B
"ker-chunkers" violate the laws of nature and will blow your equipment up.
This seems to be a cheap option (probably can get the switch box, but
it's not cheap if it blows my terminals up.

Just looking for some wisdom so I don't try to reinvent the wheel. :)

Thanks,

Fred