How They Work
Units consist of microphones and speakers that broadcast voices much like a speakerphone. They are designed so that multiple people in one room can easily hear and speak to callers without having to cluster around a telephone handset.

The equipment usually consists of an all-in-one portable unit that is placed at the center of a table and connects to a regular phone cord. Some models also have additional microphones to better capture all the voices in the room.

Sound Quality
Most regular speakerphones operate in "half-duplex" mode, which mutes the speaker whenever the microphone is activated. This is designed to prevent feedback from overwhelming a call.

However, this also creates a problem. Half-duplex severely disrupts the natural flow of conversations, since it allows only one person t o speak at a time. If anyone in the group makes a sound, the phone cuts off the voice of the remote participant. So if people speak simultaneously often, conversations can end up sounding choppy, with sentences frequently cut off.

In contrast, most conference equipment operates in full-duplex mode, allowing both parties to speak at once. The equipment uses a digital signal processor, or echo canceller, which digitally prevents feedback by eliminating the speaker sounds from the microphone pickup. Essentially, the echo canceller "hears" the speaker signals and removes this sound from the microphone input signal. Both parties can talk and listen without the awkward breaks typical of a speakerphone conversation.

Choosing a Unit
Three things to look for to ensure that you are getting the right equipment for your company are compatibility, sound quality, and office setting.

Compatibility
Setting up conferencing equipment is a simple matter of "plug and play" if a standard analog jack is available. This is not something to take for granted, however, as many companies now have digital phone systems, which are often not compatible with conferencing units. If an analog line is not available, an adapter can be used. An adapter will usually work fine, but check to see if there is interference with a unit's sound quality by its use.

Sound Quality
First, make sure your system offers full-duplex technology. While almost all models are full-duplex, some are better full-duplex than others. To test performance, have two people speak simultaneously over a phone line using the unit, each reading different passages. Under the best conditions, each participant should be able to hear the person's words clearly without any cutoffs, especially at the beginning or end of sentences.

Office Setting
Test the equipment in the environment where it will be used. That way, you can make sure the sound level is acceptable and that the microphones can reach all participants.

Options
There are a variety of options to consider according to how you plan to use the equipment. A frequent switching of the unit between different size rooms might warrant getting a model with expansion capabilities. Some units come with remote control or wireless microphones for those who want to walk around while teleconferencing.

Buying Tips
You don't have to purchase an adapter from the manufacturer. Ask a phone system dealer for a compatible adapter from a third party manufacturer; they are usually cheaper.

Rooms with high ceilings, large windows and uncarpeted floors may create a hollow sound. Test the conferencing unit in the room you will be using the most for conference calls.

If you cannot get the equipment on a trial basis, you may want to consider renting the equipment first.

Makes Available For Microphone

Koss	Logitech
Blue Microphone	Cyber Acoustics