scope:

This ETS specifies the functional protocol for the the pan-European Integrated Services Digital Network (ISDN) as provided by European public telecommunications operators for the application to a range of supplementary services at the T reference point or coincident S and T reference point (as defined in CCITT Recommendation I.411 [3]) by means of the Digital Subscriber Signalling System No. one (DSS1) protocol.

The functional protocol is based on the use of the Facility information element and the FACILITY message, as well as on other specific functional messages specified in subclause 11.1. The protocol is symmetrical, and is applicable to both the basic and primary rate access structures.

To be functional this protocol requires knowledge of supplementary services supported by the user equipment. This facilitates user equipment operation without human intervention by defining semantics for the protocol elements which user equipment can process on its own.

The procedures specified in this ETS can be used for:

- activation and deactivation;

- invocation and operation;

- interrogation;

- status request; and,

- status notification.

of supplementary services in association with existing calls or outside any existing call.

In addition, this ETS specifies the generic procedures for the channel reservation function performed by the network as it is applied by several supplementary services (e.g. call hold).

Furthermore, the functional signalling procedures that support the delivery of notifications at the usernetwork interface are covered.

The application of this ETS to individual supplementary services is outside the scope of this ETS and is defined in those standards which specify the individual supplementary services.

Further parts of this ETS specify the method of testing required to identify conformance to this ETS.

This ETS is applicable to equipment, supporting supplementary services using the functional protocol, to be attached at either side of a T reference point or coincident S and T reference point when used as an access to the public ISDN.