The present document specifies the Abstract Test Suite (ATS) and partial Protocol Implementation eXtra Information
for Testing (PIXIT) proforma for the User side of the T reference point or coincident S and T reference point (as
defined in ITU-T Recommendation I.411 [11]) of implementations conforming to the stage three standard for the Closed
User Group (CUG) supplementary service for the pan-European Integrated Services Digital Network (ISDN) by means
of the Digital Subscriber Signalling System No. one (DSS1) protocol, EN 300 138-1 [2].
EN 300 138-3 [4] specifies the Test Suite Structure and Test Purposes (TSS&TP) related to this ATS and partial PIXIT
proforma specification. Other parts specify the TSS&TP and the ATS and partial PIXIT proforma for the Network side
of the T reference point or coincident S and T reference point of implementations conforming to EN 300 138-1 [2].