If you are fighting a losing battle against a tide of keyboards, computer mice and displays in your office or home, then a KVM switch could be just what you're looking for.

These simple devices allow you to connect several computers to one screen, mouse and keyboard without the usual nonsense of Windows deciding to disable your mouse forever.

How they Work

KVM switches work by pretending to be a screen, keyboard and mouse to each of a number of computers. You connect each computer to one set of ports (Video, PS/2, ADB, USB or serial), and when the computer boots it will see what it expects to see on those ports. The computer doesn't know that you're off looking at something else, and there's no need to tell it.

The other half of the magic is some electronics which connect these ports to a single set of matching ports connected to the real devices. Obviously the switch must be made without interrupting the computers' comfortable fantasy of continuous input devices.

Switching can be manual using a rotary switch or, more usually, electronically using a button on the switch box and/or a keyboard hotkey sequence.

And that really is all there is to it.

Why You Would Want One

There are endless reasons for wanting a KVM switch. You might want to put your PCs under the stairs to keep the noise down, in which case you can run one long video cable instead of two or three. You might have a rack of servers in a computer room. You might want to reduce clutter on your desk while still using three or four computers.

The more advanced switches allow interconnection over Category 5 cabling, meaning that you can control the systems from another room or even another building. Most also allow cascading - so you can take two four-port switches to control up to seven computers (one port on one unit is the uplink to the other).

Alternatives

You can download a marvellous free utility called VNC which allows you to run a remote console on most types of computer. The only downside of this is that response lags fractionally.