access to the network but do not define any end-to-end compati- Group 3 FAX bility; and terminal NETs, which ensure network-wide compati- Group 4 FAX bility of a specific public service. The purpose of the NETs is to: Teletex 1. Ensure the safety of the user and of employees of public ISDN Terminal telecommunication network operators. 2. Protect the public telecommunication network from harm. 3. Ensure the interworking of terminal equipment, where this is justified. 4. Provide an uniform conformity testing programme, SO that 22.4.4.2 The CTS programme equipment approved in one member country can be used in another. The European Commission has also been active in supporting test tool development through projects connected with conformance Table 22.10 lists early NETs. Some of these NETs are very testing, called Conformance Test Services (CTS). This programme comprehensive, running into a thousand pages in length. is concerned with setting up test services throughout Europe SO that a vendor need only test his equipment once and receive approval for sale throughout the EC. This is covered by Memorandum M-IT-03 22.4.4.1 which allows countries within EC and EFTA to mutually recognise each other's test reports and certificates. Test laboratories are ac- At the end of 1991 the procedure for the development of NETs was credited at two levels: third party laboratories and operators of test revised. Some of the NETs were now know as Common Technical procedures, to ensure equivalence of test results. In the UK the Regulations (CTRs) and a new body was set up to be responsible for British Approvals Board for Telecommunications (BABT) is the approvals, called the Approvals Committee for Terminal Equipment responsible authority on testing and approvals. (ACTE). The ACTE represents the interests of all parties: operators, Figure 22.9 illustrates the CTS process. The rules are formulated manufacturers and users. It is advised by TRAC. CRTs consist of by the European Committee for IT Certification (ECITC), whose subsets of ETSs, 