This first part of EN 300 369 specifies the stage three of the Explicit Call Transfer (ECT) supplementary service for the
pan-European Integrated Services Digital Network (ISDN) as provided by European public telecommunications operators
at the T reference point or coincident S and T reference point (as defined in ITU-T Recommendation I.411 [5]) by means
of the Digital Subscriber Signalling System No. one (DSS1) protocol. Stage three identifies the protocol procedures and
switching functions needed to support a telecommunication service (see CCITT Recommendation I.130 [3]).
In addition, the present document specifies the protocol requirements at the T reference point where the service is
provided to the user via an intermediate private ISDN.
The present document does not specify the additional protocol requirements where the service is provided to the user via
a telecommunications network that is not an ISDN.
The ECT supplementary service enables a user who has two calls, each of which can be an incoming call or an outgoing
call, to connect together the other users in the two calls, into one call. One of the two calls shall be answered, the other
call can be either answered or, as a network option, in the alerting phase.
The ECT supplementary service is applicable to all circuit-switched basic telecommunication services using one
B-channel.
Further parts of EN 300 369 specify the method of testing required to identify conformance to the present document.
The present document is applicable to equipment supporting the ECT supplementary service, 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.