ISDN stands for Integrated Services Digital Network, which is a set of communication standards that allows simultaneous digital transmission of voice, video, data, and other network services over the digitalized circuits of the public switched telephone network. It is a circuit-switched telephone network system that transmits both data and voice over a digital line. ISDN was introduced in 1986 by BT as a replacement for old-fashioned landlines to digital lines and added features that weren’t available with a classic telephone system. The main feature of ISDN is that it can integrate speech and data on the same lines, which were not available in the classic telephone system.
ISDN provides high-speed, high-bandwidth channels to every subscriber on the public switched telephone network, achieving end-to-end digital functions with standard equipment interface devices. It provides a packet-switched connection for data in increments of 64 kilobit/s and a maximum of 128 kbit/s bandwidth in both upstream and downstream directions. ISDN is also used as a smart-network technology intended to add new services to the public switched telephone network (PSTN) by giving users direct access to end-to-end circuit-switched digital services and as a backup or failsafe circuit solution for critical use data circuits.
ISDN has been replaced by broadband internet access connections like DSL, WAN, and cable modems, but it is still used as a backup when the main lines fail. Some of the reasons people choose ISDN are:
- It offers multiple digital services that operate through the same copper wire.
- Digital signals broadcast through telephone lines.
- ISDN provides simultaneous voice, video, and text transmission between individual desktop videoconferencing systems and group videoconferencing systems.
