Integrated Services Digital Network (ISDN) - Signalling System No. 7; Digital cellular telecommunications system (Phase 2); application of ISDN User Part (ISUP) version 2 for the ISDN-Public Land Mobile Network (PLMN) signalling interface - Part 3: Test Suite Structure and Test Purposes (TSS&TP) specification (Endorsement of the English version ETS 300646-3:1998 as German Standard)