This draft European Telecommunication Standard (ETS) gives the characteristics of a Flexible Multiplexer (FM) equipment; the related functions able to handle a variety of services with transparency for the service provider@ allowing enhanced management capabilities to be used in the access network. The services considered in this ETS are related to digital leased line networks and transparent transfer of 2 048 kbit/s signals in applications such as Integrated Services Digital Network (ISDN) primary rate and access or 2 048 kbit/s ONP leased line. ISDN basic access and Public Switched Telephone Network (PSTN) may be subject to further consideration according to V5 interface standards. Tributaries of this multiplexer provide interfaces related to the services to which it is connected. Internal mapping functions are based on 64 kbit/s and n x 64 kbit/s signals. The handling of sub 64 kbit/s signals is not precluded and is considered as an option to the equipment. Also covered are the characteristics of 2 048 kbit/s aggregate frames based on CCITT Recommendation G.704 [4] and on ETS 300 167 [32] with optional path protection and 2 048 kbit/s aggregate termination based on CCITT Recommendation G.703 [3] and on ETS 300 166 [31] with optional section protection. Each aggregate frame based on CCITT Recommendation G.704 [4] and on ETS 300 167 [32] may contain multiple services. The requirements contained in this ETS are only for the purpose of describing the functions of the multiplexer and are not intended to represent actual implementations. Part 2 of this ETS covers the management of the FM which is on line with the general principles of the telecommunication Management Network (TMN).