an ideal technology for a number of applications including interconnection of a PBX to a local switch, dynamic bandwidth allocation for higher-end videoconferencing applica- tions, and interconnection between an ISP's network and that of the local telephone company. Some PBXs are ISDN-capable on the line (customer) side, meaning that they have the ability to deliver ISDN services to users that emulate the services that would be provided over a direct connection to an ISDN- provisioned local loop. On the trunk (switch) side, the PBX is connected to the local switch via one or more T1s, which in turn provide access to the telephone network. This arrangement results in significant savings, faster call setup, more flexible administration of trunk resources, and the Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Access Technologies Access Technologies ability to offer a diversity of services through the granular allocation of bandwidth as required. Videoconferencing Videoconferencing-an application that now enjoys widespread accep- tance in the market thanks to service providers like Proximity Systems and affordable, effective video CODECs from companies like PolyCom and Tandberg-has moved from the boardroom to the home office and everywhere in between. While BRI provides adequate bandwidth for casual conferencing on a reduced-size PC screen, PRI is preferable for high-quality, television-scale sessions. Its ability to provision bandwidth- on-demand makes it an ideal solution. All major videoconferencing equipment manufacturers have embraced PRI as an effective connectiv- ity solution for their products and, consequently, have designed their products in accordance with accepted international standards-specifi- cally H.261 and H.320. A typical corporate-level videoconferencing unit incorporates an inverse multiplexer (IMUX) that combines the band