scope:

This standard describes the interface between the telecommunications network and the customer installation in terms of their interaction and electrical characteristics. The requirements of this standard apply to a single asymmetric digital subscriber line (ADSL). ADSL allows the provision of voiceband services (including POTS and data services up to 56 kbit/s) and a variety of digital channels. In the direction from the network to the customer premises the digital bearer channels may consist of full-duplex low-speed bearer channels and simplex high-speed bearer channels; in the other direction only low-speed bearer channels are provided.

The transmission system is designed to operate on two-wire twisted metallic cable pairs with mixed gauges. The standard is based on the use of cables without loading coils, but bridged taps are acceptable in all but a few unusual situations.

Specifically, this standard:

− describes the transmission technique used to support the simultaneous transport of voiceband services and both simplex and duplex digital channels on a single twisted-pair ;

− defines the combined options and ranges of the digital simplex and full-duplex channels provided;

− defines the line code and the spectral composition of the signals transmitted by both ATU-C and ATU-R;

− specifies the transmit signals at both the ATU-C and ATU-R;

− describes the electrical and mechanical specifications of the network interface;

− describes the organization of transmitted and received data into frames;

− defines the functions of the operations channel;

− defines the ATU-R to service module(s) interface functions;

− defines the Transmission Convergence Sub-layer for ATM transport.

Purpose

This interface standard defines the minimal set of requirements to provide satisfactory simultaneous transmission between the network and the customer interface of POTS and a variety of high-speed simplex and low-speed duplex channels. The standard permits network providers an expanded use of existing copper facilities. All Layer 1 aspects required to ensure compatibility between equipment in the network and equipment at a remote location are specified. Equipment may be implemented with additional functions and procedures.