 work over distance, the room may need CAD interfaces, as well as the ability to convey, and incorporate mechanical and electrical drawings, materials lists, specifications, and proposal preparation systems. In addition, a phone interface for audio-only meeting participants is usually required. Audio add-on is usually provided as a feature of a videoconferencing system and requires a RJ-11 jack connection to a PBX or outside line. Videoconferencing monitors must be selected according to the application. The greater the number of participants, the larger the monitor should be. Twenty-inch monitors will support up to four conference participants. A 27" monitor can support 6-8 participants. Where eight or more participants will be involved in a meeting, a 35" monitor is preferable. Today's flat-screen monitors significantly solve the space problems that legacy CRTs created. Implementing Group-Oriented Systems Training environments, in which many viewers are involved and the room is large, often require projection systems (front or rear). In such a case, a RGB projection system need be procured. Systems in this category can use rear- or front-projection. Again, it is important to enlist the support of a professional for non-standard implementations of this nature. SCAN CONVERTERS Television monitors paint the screen using a technique known as interlace scanning. Interlace scanning divides a frame of video into two fields; one made up of odd lines and the other made up of even lines. To convey the frame, the field containing even lines is transmitted first, and the field containing odd lines is transmitted immediately thereafter. Sixty such fields are sent in a single second, which conforms to the 60 Hz electrical system used in the U.S. and Japan. This approach eliminates flicker, the shimmering effect that occurs when frames are delivered at a rate too slow to leverage human persistence of vision. PCs and workstations use video graphics adapter (VGA) and Super-VGA (SVGA) formatted signals-better known as progressive