U interface: For basic-rate access

Access network

An access network is that part of a telecommunications network which connects subscribers to their immediate service provider. It is contrasted with the core network, which connects local providers to each other...

 in an Integrated Services Digital

Digital

A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

 Network

Telecommunications network

A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections...

 (ISDN

Integrated Services Digital Network

Integrated Services Digital Network 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...

) environment, a user

User (telecommunications)

In telecommunications, a user is a person, organization, or other entity that employs the services provided by a telecommunication system, or by an information processing system, for transfer of information....

-to-network interface

Network interface

Network interface may refer to:* Network interface controller, the device a computer uses to connect to a computer network* Network interface device, a demarcation point for a telephone network...

 reference point

Reference Point

Reference Point is the first album by Acoustic Alchemy released in 1990 for jazz label GRP and their fourth album overall.Containing some of the band's more popular tracks, such as the title track "Reference Point", "Same Road, Same Reason" and "Cuban Heels", the nine-track album is also the only...

 that is characterized by the use of a 2-wire-loop transmission system

Transmission system

In telecommunications a transmission system is a system that transmits a signal from one place to another. The signal can be an electrical, optical or radio signal....

 that (a) conveys information

Information

Information in its most restricted technical sense is a message or collection of messages that consists of an ordered sequence of symbols, or it is the meaning that can be interpreted from such a message or collection of messages. Information can be recorded or transmitted. It can be recorded as...

 between the 4-wire user-to-network interface, i.e., the S/T reference point, and the local exchange

Telephone exchange

In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...

, (b) is located in the servicing central office, and (c) is not as distance sensitive as a service using a T interface.