The present document defines the stage two description of the Explicit Call Transfer (ECT) supplementary service for the
pan-European Integrated Services Digital Network (ISDN) as provided by European public telecommunications
operators. Stage two identifies the functional capabilities and the information flows needed to support the service
description as described in stage one. The stage two description also identifies user operations not directly associated
with a call (see CCITT Recommendation 1.130 [2]).
The present document is specified according to the methodology specified in CCITT Recommendation Q.65 [3].
The present document does not formally describe the relationship between this supplementary service and the basic call,
but where possible this information is included for guidance.
In addition the present document does not specify the requirements where the service is provided to the user via a private
ISDN. The present document does not specify the requirements for the allocation of defined Functional Entities (FEs)
within a private ISDN; it does, however, define which functional entities may be allocated to a private ISDN.
The present document does not specify the additional 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 or an outgoing call,
to connect the other users in the two calls.
The ECT supplementary service is applicable to all circuit-switched telecommunication services.
The present document is applicable to the stage three standards for the ISDN ECT supplementary service. The term "stage
three" is also defined in CCITT Recommendation 1.130 [2]. Where the text indicates the status of a requirement, i.e. as
strict command or prohibition, as authorization leaving freedom, as a capability or possibility, this shall be reflect (...abbreviated)