標準號：SIS SS-NET 1-1989
中文標準名稱：對連接到電路交換公共數據網絡和使用CCITT推薦X．21接口租用線路的數據終端設備的審批要求
英文標準名稱：Approval requirements for data terminal equipment to connect to circuit switched public data network and leased circuits using CCITT Recommendation X.21 interface
發布日期：1989/9/13 12:00:00
實施日期：1999/12/31 12:00:00
適用范圍：This NET contains requirements for the type approval of data terminal equipment employing CCITT Recom-mendation X.21 [1] interface to circuit switched public data networks and leased circuits. The requirements are intended to ensure that the service available to other users of public telecommunications systems is not interfered with, nor that any public system will be adversely affected. Safety requirements are included for protection of personnel operating the public telecommunications systems.This NET is applicable only if the relevant user classes of service are being provided by the Administration concerned. It does not impose any obligation on Administrations to provide any particular user class of service.Annexes (and their Appendices) to this specification are an integral part of this specification.1 Although the title and scope of the NET appear to limit the application to cover only data terminal equipments, such equipment may cover applications other than data (for example, voice in Italy, voice and video in France, and public telephony service in the UK). Similarly, the apparent limitation to cover access only to public data networks does not preclude access to digital networks supporting both data and telephony services, as in the UK.2 The application of this scope clause is limited by statements in Clause 6. It is the intention to consider optional features and optional facilities for inclusion in a future issue of this NET. In the meantime, where a network service includes such optional elements and a terminal equipment is designed to make use of them, published national requirements may apply (and may require additional tests).3 The implications, if any, of the use of terminal adaptors to provide the CCITT Recommendation X.21 [1] service interface has not been considered in the drafting of this NET.