Basic Rate Interface

The base port is the default port of the digital ISDN telecommunication network. Common abbreviations for the base terminal are: BA, BAs and BRI ( basic rate interface engl. ). It is mainly used by private customers or small businesses. Larger companies with a high volume of telephone calls simultaneously use instead usually the primary rate access.

Channels and bandwidth

A basic connection provides two bearer channels (B channels, of Engl. Bearer ) with 64 kbit / s and a signaling channel (D-channel, of Engl. Data) with 16 kbit / s The net data transfer rate is: 2 × 64 kbit / s 16 kbit / s = 144 kbit / s


The Basic Rate Interface consists of two sections:

  • The local loop (ULL ) between the local exchange ( or the remote peripheral unit ) and the NT ( network termination ) in the house. It is usually a UK0 interface consists of a pair of copper wires and belongs to the network operators (eg Deutsche Telekom, Versatel, ...).
  • The in-house wiring, which is designed as a bus and connects the terminals to the NT. It is called S0 bus and consists of two pairs. It belongs to the connection owner, who is responsible for their function itself.


Multipoint connection

The multipoint connection ( point to multipoint ) is in private households, the most common mode of operation. Several terminals (TE ) can be directly connected to the S0 bus, get assigned from the values ​​between 64 and 127, the ( few exceptions ) from the central office dynamically up to eight Terminal Endpoint Identifier ( TEI ).

System connection

At the system connection (point to point ), only one device (usually a PBX ) can be connected. The terminal is connected to the S0 bus and receives the fixed TEI value 0 because of the different TEIs no devices can be operated in the system connection mode, intended for the mode -multipoint connection.

Multipoint - to-point connection

The multipoint - to-point connection is an Austrian special variant that is with Austrian firmware rarely offered today due to lack of hardware. With appropriate telephone systems have multiple phone numbers can be assigned to a base terminal (for example: private / company ) and still be elected by different employees. The possibilities of the first two variants are presented here in total, for example, different night and circuits in response to the redirection number. The omission of this variant is justified with EU directives on unifying the systems.

  • ISDN