-performance proprietary algorithms, the differentiators in the standards-based codec world are implementation and how fast vendors offer new codecs (e.g., H.264). Group systems sell for anywhere between $3,000-50,000 (although one could conceivably use a $1,000 personal or even a $50 webcam for a group application). The additional for boardroom systems anymore primarily reflects aesthetics since most boardroom systems features are now available in set-top units. Still, boardroom systems have an edge in features. The price spread reflects differences in the following areas: Group Systems Number and type of audio and video compression algorithms supported (H.261, H.263, H.264 G.711, G.722, G.728, G.729, G.729A) Picture resolutions supported (e.g., 4CIF, CIF, QCIF) Frame rates supported (60 fps high-end, 30 fps mid-range, 15 fps low-end) Network interfaces offered (e.g., Ethernet, USB, V.35/RS-530/RS-449 with RS- 366 dialing, ISDN with NT-1 adapters, CSUs and inverse multiplexers) Transmission speeds supported (256 Kbps-2 Mbps) Audio-related features (e.g., microphones included, mixer, surround sound or stereo surround). Cameras (e.g., number and type included, lines of resolution, sensitivity to light, features such as voice-activated camera movement) Monitors (e.g., size, number, and resolution) User interface Security (e.g., secure password authentication, embedded AES encryption, H.233, H.234, H.235v3) Multipoint capabilities Peripherals (e.g., scheduling software, document camera, scan converter, inverse-multiplexer) Ongoing maintenance and support, and upgrade policy The remainder of this chapter addresses the subtleties of these system components and features. Understanding the differences will help prospective buyers make accurate systems comparisons. AUDIO AND VIDEO COMPRESSION ALGORITHMS Group-oriented systems should support H.320 (including G.728 compression for low-bandwidth audio encoding), the ITU-T's H.231/H.243 protocols, and the T.120 data conferencing specification. An H.320 system should be able 