Integrated Services Digital Network (ISDN) 

Is a set of communications standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network.
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 analogue phone can provide. It offers circuit-switched connections (for either voice or data), and packet-switched connections (for data), in increments of 64 kb/s.

Gigaset PRO devices that support ISDN

• Gigaset DX800 (ISDN2 only / Multipoint protocol)
• Gigaset T500/T300 PRO using PCI cards
• Gigaset T640 4 ISDN2 lines and Gigaset T440 2 ISDN2 lines

Gigaset T500/T300 PRO ISDN PCI cards

There are 2 different type of cards that are supported.

1. Sirrix
2. Digium

It is not allowed to use a mixture of Sirrix and Digium cards, as driver problems will occur.