Networking

Consider functionality, cord length, and sound before suggesting a KVM switch

When you or your end users work on multiple PCs, there's no better way to save desk space than with a KVM switch. But before spending a dime on equipment, find out how switch functionality, cord length, and sound support should affect your decision.


Around the first of the year, I realized that my computer room was becoming too crowded to remain a productive environment. To save space, I went to Space Savers and bought a wire rack with a 1,700-pound-per-shelf capacity and moved my 16 computers onto the rack. I then left one desk in my computer room with four sets of mice, monitors, and keyboards. I attached each set to a group of four PCs via keyboard/video/mouse (KVM) switches. The end result helped me save a lot of space and made my home office into a much more comfortable environment.

While KVM switches have been used in server rooms for years, these handy devices are frequently connected to end-user desktops. As the cost of computer hardware has come down, an ever-increasing number of users are working from multiple computers. And unless these users want a desk full of keyboards, monitors, and mice, a KVM switch is a necessity.

But before you reorganize your multicomputer users, there are some issues that you should consider when using KVM switches. In this article, I’ll explain how switch functionality, cord length, and sound can make or break a KVM implementation.

Switch functionality
The first issue that you must contend with is functionality. Some lower-end KVM switches are nothing more than a switch in its simplest form. The problem with these low-end switches is that after awhile, the computers that you aren’t using tend to think that no keyboard or mouse is attached. When you switch back to that computer, the computer may or may not recognize the existence of the keyboard or the mouse.

To get around this issue, I chose to use a series of Belkin OmniView SOHO KVM switches. What I liked about the Belkin switches is that they are designed to keep a load on all keyboard and mouse connections so that the computer never notices that the keyboard or mouse has been unplugged.

The second functionality issue that you may encounter is that some LCD flat panel displays don’t work well with KVM switches. I have a Proview LCD screen that works great with them, but I have a Sony LCD panel that doesn’t work so well with the switch. Occasionally, when I switch computers, the video is cut in half on the screen. This only happens occasionally, and the only way that I’ve found to get around the problem is to turn off the screen before switching to a different computer. However, I've noticed that the problem occurs only when switching between PCs that are running at different video resolutions.

Cord lengths
Another issue that you might run into is cord length and quality. Most monitor manufacturers recommend that VGA cables don’t extended farther than 20 feet. When you use a KVM switch, you must remember that you have one cable connecting the monitor to the switch and another cable connecting the switch to the PCs. So your VGA cable length is the sum of the two cables. If you use a very high-quality cable, you can extend a VGA cable farther, but you’ll usually experience a flicker unless you stick to using lower resolutions and refresh rates. I’ve seen a VGA cable extended for a total of 50 feet using high-quality cables and low resolutions.

I recommend using Belkin-brand cables, each of which shouldn’t exceed 10 feet (for a maximum of 20 feet between the PC and the keyboard, monitor, and mouse). The Belkin cables can be expensive, costing around $20 for every PC that you want to attach to the switch. While much cheaper cables are available, I’ve found that using higher quality cables virtually eliminates video quality problems associated with signal degradation or radio interference. In Figure A, you can see that I had no problems attaching an entire rack of PCs to a nearby workstation using 10-foot cable segments.

Figure A
This entire rack of PCs is connected to a single desk via 10-foot cables and a set of KVM switches.


Sound support
Another thing that I really like about Belkin's KVM switches is their support for sound. Each port on my KVM switches has a speaker jack and a microphone jack. By using these ports, you can pass the sound from each PC through a common set of speakers, and you can use a single microphone with multiple PCs.

To save space, I purchased flat panel displays that had integrated speakers. As I select a PC through the KVM switch, the PC’s sound is automatically passed through the monitor’s speakers. The exception to this is that I have a high-end set of speakers attached directly to the PC that I use for multimedia production. You could attach a set of speakers directly to the KVM switch, but the KVM switch includes only analog speaker jacks, and my high-end speakers are digital. So if your users have digital speakers, don’t plan on being able to attach them directly to a KVM switch.

Planning is the key to success
Using a KVM switch can save space and help boost productivity. However, it pays to do some planning before putting one on a user's desk.

When discussing the installation of a KVM switch with an end user, alert them to the three issues I outline here. Let them also know that occasional glitches are par for the course when it comes to these switches, and there may not be a 100 percent effective fix for every problem, especially if you can't control the brand of equipment to which the user connects the switch. This will help the user to have realistic performance expectations and may save you both some frustration.

While I use and highly recommend Belkin products, manufacturers such as APC, Avocent, Cables To Go, CompuCable, End Design, Linksys, Rose Electronics, and Tripp Lite also produce KVM switches and cables. To find other manufacturers, check out this list from CNET Shopper.com.

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