Integrated Services Digital Network (ISDN); Call Waiting (CW) supplementary service; functional capabilities and information flows; english version ETS 300057:1992
Integrated Services Digital Network (ISDN) - Signalling System No.7 (SS7) - ISDN User Part (ISUP) version 4 for the international interface - Part 17: Call Waiting (CW) supplementary service [ITU-T Recommendation Q.733, clause 1 (1992), modified]
