INTRODUCTION AND SCOPE

The standards contained in this document are intended to be used as performance and interface criteria. As such, these standards may find a typical application in the layout of a communication system incorporating other types of equipment (such as cable or radio equipment). An added purpose of these standards, however, is to furnish a basis for the user to evaluate and specify TDM equipment on a terminal or back-to-back basis.

It is recognized that the different requirements of systems result in more or less rigorous requirements for TDM equipment. It is one of the objectives of this document to assist the user in selecting the TDM equipment for his specific system needs.

These standards apply to TDM equipment between the 4-wire audio frequency terminals and the terminals which interface with the transmission medium. The terminals which interface with the transmission medium are referred to in this standard as the TMI (Transmission Medium Interface) and represent the output of the highest level of time division multiplex. Wiring, signaling, and other office equipments are specifically excluded from these standards. Where interconnects between TDM equipment of different types are not anticipated, it is only necessary to specify end-to-end performance and interface parameters at the audio and transmission medium terminals. These parameters are contained in PART I of this document. Where interconnects between different types of TDM equipment are planned, however, many additional parameters need to be considered. These parameters are contained in PART II of this document.

Two types of multiplex equipments are considered in this standard.

Class I multiplex is intended primarily for use in multiple link (Built-up) circuits and/or long-haul circuits.

Class II multiplex is intended for use in those applications which do not justify Class I equipment. Class II equipment may be used in tandem with Class I equipment but is not normally intended for use in tandem with more than one other set of Class II equipment.

At present the following requirements apply to Class II equipment only. Requirements for Class I equipment will be added at a later date.