Integrated Services Digital Network (ISDN) - Call Hold (HOLD) supplementary service - Digital Subscriber Signalling System No. one (DSS1) protocol - Part 1: Protocol specification; english version ETS 300141-1:1992
Integrated Services Digital Network (ISDN) - Call Hold (HOLD) supplementary service - Digital Subscriber Signalling System No. one (DSS1) protocol - Part 1: Protocol specification (Endorsement of the English version EN 300141-1 V 1.2.4 (1998-06) as German standard)— 1 стр.
Integrated Services Digital Network (ISDN) - Explicit Call Transfer (ECT) supplementary service - Digital Subscriber Signalling System No. one (DSS1) protocol - Part 1: Protocol specification
