This chapter provides you with some background information about ISDN, including information about: • analog vs. ISDN • type of ISDN service •ISDN l ayer s • ISDN bearer capability • services and features for ISDN PRI and BRI • ISDN hardware • ISDN standards compatibility Integrated Services Digital Network (ISDN) technology provides a fast, accurate, and reliable means of sending and receiving voice, data, images, text, and other information through the telecom network. ISDN uses existing analog telephone wires. The signal on the wire gets divided into separate digital channels, which dramatically increases the bandwidth. ISDN uses a single transport to carry multiple information types. What once required separate networks for voice, data, images, or video conferencing is now combined on to one common high-speed transport.