scope:

This Technical Basis for Regulation (TBR) specifies the technical characteristics (electrical and mechanical interface requirements) and access control protocol to be provided by packet mode terminal equipment intended for connection to a dedicated interface of a Packet Switched Public Data Network (PSPDN) using CCITT Recommendation X.25 [1], [2] and [3] making use of Link Access Procedure Balanced (Modulo 8 operation) (LAPB) and Link Access Procedure Balanced (Modulo 128 operation) (LAPB Extended) modes of operation.

The objective of this TBR is to ensure that no disturbance occurs to the public network, and to ensure interworking between network and terminal, but without any guarantee of terminal operation and end to end operability across networks.

This TBR contains the minimum set of requirements derived from CCITT Recommendation X.25 [1], [2] and [3] in accordance with prior European harmonisation documents (NET 2, see annex D). The requirements of this TBR are suitable for testing terminal equipment for connection to CCITT Recommendation X.25 [1], [2] and [3] (1980, 1984, and 1988) PSPDNs. Terminal equipment that is capable of either originating only or terminating only, packet level modes of operation have been included. Data Terminal Equipment (DTE) which satisfies the relevant technical requirements of this TBR may be connected to every PSPDN, use any of the essential (E) facilities and invoke any of the provided additional (A) facilities as given in CCITT Recommendation X.2 [4] and [5].

For each requirement in this TBR, a test is given, including measurement methods. Requirements apply at the public network interface of the terminal equipment, which may be stimulated to perform tests by additional equipment if necessary. For the purposes of this TBR a terminal equipment comprises of that apparatus included between a PSPDN Network Termination Point (Data Circuit Terminating Equipment (DCE)), and the terminal equipment boundary point that delimits the Network to Transport layers as defined in ITU-T (CCITT Recommendation X.200) subclause 7.5 (Reference model of Open Systems Interconnection). Equipment in this context is taken to mean either software, firmware or hardware.

Where the packet mode terminal equipment supplied for test does not contain the functions of layers 1, 2 and 3 (as defined in ITU-T (CCITT Recommendation X.200) subclause 7.5 (Reference model of Open Systems Interconnection)), the terminal's documentation and instructions for use shall state which additional equipment is required for compliance to this TBR and the additional equipment shall be submitted for test, as though all the functional layers were provided by the packet terminal equipment.

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

Terminal equipment may be subject to additional or alternative attachment requirements in other 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.