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 2: Protocol Implementation Conformance Statement (PICS) proforma specification (Endorsement of the English version ETS 300646-2:1998 as German standard)