ISDN layer 1 to 3 implementation

The authors discuss the integrated services digital network (ISDN) as an attractive network evolution from existing telephony to support a wide range of both voice and nonvoice telecommunications services. Significant efforts have been devoted to the development of a common European approach and supporting international standards. ISDN interfaces promise a common access method to bearer services (switched and nonswitched) and to teleservices (such as telematic services, at least initially), with both sets of services optionally complemented by supplementary services. Business customers, which are the main potential ISDN users, require international availability of ISDN services with harmonized tariff principles and a high degree of consistency in connecting devices to their international networks. A number of specific ISDN standardization problems are addressed