What does ISDN stand for?

ISDN stands for Integrated Services Digital Network. It is a group of telecommunications standards designed to transmit voice, video, fax, and computer data digitally over the public telephone network.

ISDN emerged as telephone companies began replacing analog switching systems with digital technology. Work on the standard began around 1980, and it was formally standardized internationally in 1988 through the CCITT, now known as the ITU-T. Its goal was to provide several digital services through one telephone connection rather than requiring separate specialized lines.

A Basic Rate Interface, or BRI, commonly used two 64-kilobit-per-second bearer channels plus a signaling channel, often described as 2B+D. This allowed users to make a call while transmitting data on the other channel. ISDN was important for early video conferencing and faster dial-up-era internet access, but it was eventually overtaken by DSL, cable broadband, fiber, and internet-based phone systems. “Integrated services” refers to carrying multiple kinds of communication over the same digital network.