On Sat, 12 Jun 2021 02:13:03 +0000 (UTC),
wrote:

I've never seen KVM switches needing power before and this one (I bought
several) has no power supply included. But their is a socket for a power
adaptor. Zonet KVM3304.

This one?
https://www.amazon.com/Zonet-4-Port-KVM-Switch-cables/dp/B000KUWXCS
"Each unit comes with a set of 4 PS/2 cables, each cable is 3 feet
long. No power supply is needed.... each switch draws its power
directly through the cables that attach to the desktop."

The KVM3304 gets its power from the computer USB port. If you don't
have at least one USB cable plugged into a computah USB port, it won't
power on. I stupidly bought one of these on eBay without the cables.
Big mistake. The designers of this abomination decided to save on the
cost of the USB connectors and instead ran the USB data and power
through each of the 4 video cable. Without these special cables, it
won't work.
https://i.ebayimg.com/images/g/PLYAAOSw4f9f9g8k/s-l1600.jpg
https://www.rackmountsolutions.net/ce-10-combo-3-n-1-kvm-cable-10-ft/

So before I swithc everything over and find out it
doesn't work, I was hoping someone would tell me if I really need power and
what happens when I don't have it. ie, maybe I should shut down a few of the
machines. THis thing is 4-way. What's a KVM - Keyboard Video Monito switch
that lets you use multiple computers with one console.

Did you get the cables with the KVM3304?

According to several web pages and listings the power supply is 9VDC
500ma. However, if you have the correct cables, you shouldn't need an
external power supply.


--
Jeff Liebermann
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558