scope:

This Technical Basis for Regulation (TBR) specifies the technical characteristics (electrical and mechanical interface requirements, and access control protocol) to be provided by terminal equipment to be connected to Circuit Switched Public Data Networks (CSPDNs) and leased circuits presented at a CCITT Recommendation X.21 [2] interface, or at an interface physically, functionally and electrically compatible with CCITT Recommendation X.21 [2] but operating at any data signalling rate up to, and including, 1 984 kbit/s. The objective of this TBR is to ensure that no disturbance occurs to the public network.

This TBR contains the minimum set of requirements derived from CCITT Recommendation X.21 [2], in accordance with prior European harmonization documents (NET 1). These include circuit switched service and leased circuits for point-to-point connection for various user classes of service.

NOTE 1: Not all applicable user classes and services are available in all countries.

The multipoint service is not included in the minimum set. Not all optional features and facilities defined in CCITT Recommendation X.21 [2] are included in the minimum set.

A test is given for each requirement in this TBR, including measurement methods. Requirements apply at the public network interface of the terminal equipment, which may be stimulated to perform the tests by additional equipment if necessary.

This TBR also gives guidance on appropriate standards relating to the essential requirements on safety.

Terminal equipment may be subject to additional or alternative requirements in other Common Technical Regulations (CTRs) depending on its functionality, in particular if it supports a service which is considered a justified case for regulation of terminal equipment interworking via the public telecommunications network.

NOTE 2: Although this TBR provides a means of approving terminal equipment for connection to public networks operating at any data signalling rate in a continuous range up to 1 984 kbit/s, the choice of data signalling rates within this range offered by a particular public network is determined by the operator of that network.