Effects are another big consideration. Generally, the greater the cost of the switcher, the greater the number of effects it has built-in, but this isn't always true-- with some switchers, you're paying for durability, not a myriad of flashy effects. Typically, video switchers allow for chroma key effects, a variety of wipes and pattern dissolves, and the ability to do titles. Some mixers allow for a variety of chroma colors, others less so.

Some units feature a beats per minute (or "B.P.M." as all the cool hip-hop guys like to say) display to allow VJs in clubs to sync-up transitions and effects to the beat of the music that's playing. Others also include a MIDI-input, allowing the switcher's effects to be remote-controlled using MIDI (Musical Instrument Digital Interface), which happens to be the common language of electronic musical instruments.

Lower-end machines often lack chroma key, but typically have luminance control for inserting simple titles into a project. These types of low-end mixers also may lack preview outs. But since they typically offer very simple effects, there's little need to preview.

The Focus Enhancements MX-4 is a well-equipped mid-priced switcher capable of producing a myriad of video effects. An audio mixing feature is also present. In combination audio- video mixers, listen for good audio sync. The MX-4 also includes a T-bar control, which, as we'll discuss in a moment, may be an important feature for you.

Finally, what many consider to be an important control feature will require some thought. First of all, T-bars are infamous for being bumped if the switcher is in a crowded area. The bar protrudes in such a way that can be caught on a pants pocket or coatsleeve. A good rule of thumb is to not have any two "bars" together; keep the T-bar away from the martini bar.

Some users, especially when they are doing VJ-style productions, prefer the quicker response of a fader, as opposed to the slow, but more precise feel of a T-bar. In any case, the pacing of an event may determine your choice. Again, it helps to know what types of material the switcher will primarily be used for. Numark's AVM01 streets for less than $1,000, and lacks a T-bar, but is an extremely popular switcher with the VJ set.

So, how to best assimilate this information? You'll benefit the most by knowing your own projects, but leave yourself some room for expansion. See what others are using, and for what purposes. Don't forget to consider the environment in which you'll use it; indoor, outdoor, studio, or travel. Think of wear and tear if you have to set up and tear down often if you don't have a dedicated control room.A fair amount of decision-making will go into your purchase, but it'll pay off with a switcher built for your needs.

Ed Driscoll is a freelance journalist covering home theater and the media.

• Analog Way: www.analogway.com
• Datavideo: www.datavideo.us
• Echolab: www.echolab.com
• Edirol: www.edirol.com
• Focus: www.focusinfo.com
• FOR-A: www.for-a.com
• Grass Valley: www.thomsongrassvalley.com
• NewTek: www.newtek.com
• Panasonic: www.panasonic.com
• Ross Video: www.rossvideo.com
• Sima: www.simaproducts.com
• Snell & Wilcox: www.snellwilcox.com
• Sony: http://bssc.sel.sony.com
• Videotek: www.videotek.com