Integrated Services Digital Network is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network.
In Australia, ISDN services can either be a basic rate service, known as ISDN 2 or a primary rate service, known as ISDN 10/20/30.
Currently being phased out across the country with the rise of NBN
Prior to ISDN, the telephone system was viewed as a way to transport voice, with some special services available for data. The key feature of ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system.
ISDN is a circuit-switched telephone network system, which also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in potentially better voice quality than an analog phone can provide. It offers circuit-switched connections (for either voice or data), and packet-switched connections (for data), in increments of 64 kilobit/s.
A basic rate service provides users with two 64 kilobits per second (kbit/s) channels, which can be combined to make a 128 kbit/s channel. The basic rate service can carry voice and data traffic simultaneously and was intended to be utilised by home users and by small and medium sized businesses.
A primary rate service provides users with ten, twenty or thirty 64 kbit/s channels allowing for a maximum data rate of approximately 2 megabits per second (Mbit/s). Primary rate services are generally used by medium to large sized businesses.