ISDN
From The Glossary of Digital Photography
An abbreviation for Integrated Services Digital Network. A circuit-switched telephone network system governed by an international set of standards. Established to allow higher-speed digital data transmission over standard two-wire telephone lines, ISDN requires the use of specialized equipment at both ends of the phone line. It is commonly used as a connection to the Internet and allows faster speed than traditional dial-up access. It also allows two simultaneous connects over the same phone line. A user can thus have standard telephone operation and be connected to the Internet over the same two-wire phone line. For many uses, DSL (digital subscriber line) has replaced ISDN.
