Integrated Services Digital Network (ISDN) - Digital Subscriber Signalling System No. one (DSS1) protocol; Basic call control; enhancement at the "b" service entry point for Virtual Private Network (VPN) applications - Part 2: Protocol Implementation Conformance Statement (PICS) proforma specification (Endorsement of the English version EN 301060-2 V 1.1.3 (1998-11) as German standard)