Integrated Services Digital Network (ISDN) - Digital Subscriber Signalling System No. one (DSS1) and Signalling System No. 7 (SS7) protocols; Call Forwarding on Not Reachable (CFNRc) supplementary service for Cordless Terminal Mobility (CTM) phase 1 - Part 1: Protocol specification (Endorsement of the English version EN 302094-1 V 1.1.3 (1999-09) as German Standard)