Using KVMs


Most people own only one computer, or at least they operate only one computer at a time. After all, you can always multitask on a computer; that is, perform more than one operation simultaneously. For example, you might have a file downloading in the background while you check email in the foreground.

Conversely, some people have to operate multiple computers at once, sometimes a great number of them. Scientific analysis and computer modeling are often done on multiple computers simultaneously, and video-production houses might need to encode video on several systems at once. When you’re short on physical space, or simply don’t want to run from one system to another to check each one’s status, you need to be able to control multiple computers from a single console.

Sometimes you need to operate multiple computers at once but don’t want to pay for multiple keyboards, monitors and mice to go with them. One possible scenario is in a computer factory where technicians test run, or burn in, lots of systems at once, perhaps even hundreds of them, to weed out any failures before they’re boxed up and shipped out to customers. Another situation might be in data centers where multiple servers are running but there’s no need for each one to have its own permanent keyboard, display and mouse. In the home, you might want to connect a notebook computer to your desktop computer’s full-size display and keyboard…

So, how do you control multiple computers from a single keyboard, monitor and mouse? The solution is a Keyboard Video Mouse switch, or KVM for short. A KVM lets you do just that—control multiple computers from a single keyboard, monitor and mouse. Some KVMs even allow the sharing of speakers, USB printers and other peripherals.

To use a KVM you simply connect a keyboard, monitor and mouse to the KVM, along with peripherals such as speakers and a printer if necessary, and then connect all the computers that need controlling to the KVM. Depending on the unit, the user then presses buttons on the KVM, uses special keyboard commands or uses an on-screen display to select which system to connect to.

The main differences between KVMs are the number of computers that can be connected and how they connect to the KVM. B&H carries KVMs with 2, 4, 8 and 16 ports. Some can be daisy-chained to another KVM to control even more computers. The most economical KVMs use the same types of cables as the peripherals. For example, a VGA monitor would connect to the KVM via a VGA cable, as would the graphics outputs from the computers you’re connecting. Likewise, a PS/2 keyboard would plug right into a PS/2 input on the KVM and the PS/2 keyboard outputs from the computers would plug into PS/2 keyboard inputs on the KVM. A USB mouse would plug into a USB port on the KVM, and so on. While economical, the extensive wiring on this type of KVM can get messy, especially when dealing with more than two computers.

Neater wiring can be had when using KVMs with proprietary cabling. This type of cabling has one large connector that plugs into the KVM on one end and individual connectors on the other end that plug into a computer’s keyboard, monitor and mouse outputs. The downside of this type of KVM is that the proprietary cables can be expensive, although they are usually included with the KVM.

Another thing to consider when purchasing a KVM is the type of ports it has. If your computers have VGA video outputs and PS/2 keyboard outputs, then you obviously need a KVM that features those connectors. The same applies for DVI, DisplayPort, HDMI and so on. All you have to do is select a KVM that features the types of connectors you need—and you’re in business.

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