ISDN is a telephone network that can send voice and computer messages. ISDN is an abbreviation for `Integrated Service Digital Network'. an ISDN phone line. Integrated Services Digital Network. Integrated Services Digital Network a system that is used to send computer information at very high speed along an electronic wire similar to a telephone line. in full Integrated Services Digital Network Digital telecommunications network that operates over standard copper telephone wires or other media. ISDN connections are used to provide a variety of digital services to customers, including digital voice telephone, fax, e-mail, digital video, and access to the Internet. A wide range of data transfer rates are available, with speeds up to about 128 kilobits per second (kbps). ISDN is faster than an ordinary dial-up connection (at about 56 kbps), but much slower than cable modem or DSL connections (which typically exceed one megabit per second)
standard for digital telephone lines which allows high-speed data transfer (Telecommunications)