r 128Kbps. You could do this at smaller sites and for remote access (e.g., for telecommuters). BRI 0B+D for packet data-One 16Kbps D-channel can be shared by up to eight devices. BRI OB+D makes use of 9.6Kbps of D-channel capacity to support low-speed data terminals. This requires a terminal adapter that encapsulates the user data in D-channel frames. Applications for BRI OB+D include credit card terminals and automatic teller machines. ISDN DSL (IDSL)-IDSL delivers full-duplex, dedicated data services; it does not support voice services. It is provided either on a 1B or a 2B config- uration (i.e., 64Kbps or 128Kbps). IDSL is compatible with existing digital loop carrier systems, which serve 30% to 40% of the U.S. population. Digi- tal loop carriers are especially common in remote rural areas. Some of the DSL services (which are discussed in Chapter 12, "Broadband Access Alter- natives") are incompatible with these older-generation digital loop carriers. IDSL, however, is compatible with them, so it can be used to deliver digital private-line service at speeds up to 128Kbps. In today's environment, 128Kbps is definitely not a desired speed, SO even though IDSL can facili- tate some speedier communications than standard dialup, it is nowhere near what other broadband access options have to offer, making it an anti- quated solution. Packet-Switched Networks Packet switching was developed as a solution for the communications implications of interactive processing; it was designed to support bursty data traffic, which stays connected for a long time but is associated with low data volumes. Packet switching involves the application of statistical multiplexing, whereby numerous conversa- tions can make use of one common communications channel, which significantly Chapter 7 Wide Area Networking increases transmission efficiency. (Chapter 1, "Telecommunications Technology Fundamentals," discusses statistical multiplexing in more detail.) However, sharing a communications link introduces latency. A key issue that we are c