Caveat emptor, buyer beware. It's good advice in any transaction. This column is intended to put you in control of the buying process and to make you an informed consumer of videoconferencing products for your events. Know your needs up front, perform these tests, and the seller will beware of you!

To begin, figure out what you plan to do before you call your first supplier. Specifically, who will be talking to whom in what venues? Develop a brief list of what product attributes your applications demand:

* Talking heads or high-impact event? Is this a quick chat or a major event?

* Point-to-point or multi-point? If multi-point, you need a bridge provider.

* What bandwidth and type of telephony? "ISDN at 384k running 30fps [frames per second]" is a typical response for good-quality video over telephone lines.

* Standards or proprietary compression? If you are using dissimilar videoconferencing systems, it must be a standards-based call.

* What auxiliary devices will you need? Big events need more cameras, more speakers, more people, and, surprise, more money. Unless you're using the very latest monitor technology, you will need scan converters to show PowerPoint from a PC. No matter what, arrange to have the session videotaped.

At the Demo If you don't already know the products and vendors under evaluation, then you'll want a demonstration, in an environment as close to the actual application as possible. It's your career, not theirs, right?

Testing Audio. The key variable in the perceived quality of a videoconference is the audio. If it sounds good, it looks better! Simple tests, conducted from the end that will do most of the talking, include:

* Say (and sing!) your ABCs. Listen for consonants being slurred into aural oatmeal.

* Speak at the same volume at different distances from the mike(s): Repeat the same phrase at the same volume from 3 feet, 6 feet, 12 feet, and 30 feet away. Top-shelf equipment will smooth out a lot of the volume variations while lesser-quality microphones will be optimized for a particular distance.

* Test echo cancellation and noise suppression characteristics of the microphone you are counting on the most: In a big room, create an echo (yodeling is fun). If you expect a lot of ambient noise, conduct the demo while banquet staff sets up another event.

Testing Video. Try these exercises: * Test the system's speed with fine motions. Wiggle your fingers from a fairly deep zoom-out and see if the codec can keep up with you. The codec translates analog signals into a digital format.

* Test the codec with gross motions: Stand up, raise your hands high, and wave your body back and forth. Expect the codec to break up your image into small blocks that move at slightly different rates.

* Test the synchronization of the audio and video signal by having the far end simultaneously count out loud and hold up their fingers.

* Force the camera to re-focus quickly: Manipulate the far-end camera with drastic zooms and pans that force the image to re-focus. Then take two aspirin.

Who's Driving . . . And How? Drive the system's remote control. If you won't be hiring a skilled keypad operator, you need to know how the keypad works. Is it laid out intuitively? Are the near-end/far-end controls distinguishable? Do the pan/tilt/zoom controls do what they say they do? Beware: There are 30fps products on the market with attractive price points and utterly unusable remotes.

When you start using simple tests like these, vendors will know immediately they are working with an informed buyer.