Overview

Integrated Services Digital Network (ISDN) is a circuit-switched telephone network system that provides high-quality end-to-end digital connectivity at high rates over copper wire.

ISDN transmits all information in the digital form. It enables a single pair of telephone wires to transmit data and voice simultaneously at high rates. This feature enables ISDN to provide more services and higher transmission efficiency than PSTN, where information is transmitted in the analog form.

ISDN provides a set of standard multipurpose user-network interfaces (UNIs). Different services and terminals can use the same UNI interface to access an ISDN network.