Gives requirements for apparatus connected to particular private digital circuits, according to CCITT G-series Recommendations, operated by certain public telecommunication operators, either directly or by means of a connection to relevant branch systems for particular private digital circuits. Includes sections on general, connection and service requirements, marking, information to be provided by the supplier, tests for compliance to the 2048 kbit/s and 8448 kbit/s service, connection characteristics for relevant branch systems, rationale for the derivation of the output jitter and the application of jitter planning rules in simple point-to-point on the configurations of apparatus.