Today, we're wrapping up our look at the evolution of ISDN and why it didn't do well in the marketplace. This newsletter will look at the legacy of ISDN.The\u00a0Primary Rate Interface (PRI), we believe, is alive and well, especially for delivering traditional voice channels to PBXes. Of course, this will be a limited lifetime as the world slowly makes the transition to VoIP. Some companies also use PRI circuits to backup their data network.The Basic Rate Interface (BRI) is a different case. It is difficult to find much deployment of BRI today. For example, Steve dropped his residential ISDN service like a hot potato as soon as DSL service became available. In fact, he can cost-justify having both residential ADSL and cable modem service for less than the price of BRI service.The most active BRI usage today is not called BRI. As it turns out, most service providers now offer a lower-speed basic DSL service.\u00a0Guess what? It's essentially that nailed up BRI with 128K bit\/sec of packet data that was advocated many years ago. And there's probably a little bit of BRI still around for video conferencing, even though 128K bit\/sec is hardly sufficient for what most of us would consider to be business-quality video.At the same time, it is sometimes difficult to fully retire old protocols. Let us know how you are using ISDN today and when you're planning to turn the lights out on your ISDN services, and we'll share your comments.