• Directory of Internet terms
  • Isdn — Abbreviation for Integrated Services Digital Network. A type of digital telephone service, used for transferring large chunks of data to and from the Internet without a Modem. Gradually falling out of use these days with the introduction of ADSL broadband services. ISDN lines normally operate at 128 Kbps, which is faster than a standard 56Kbps Dial-up Modem but slower than an ADSL connection, which runs at a speed of at least 1Mbps. See ADSL, Broadband, Kbps, Leased Line.