Call Completion Supplementary Services: Completion of Calls to Busy Subscribers - Series I: Integrated Services Digital Network; Service Capabilities - Supplementary Services in ISDN Study Group 1; 29 pp
Call Completion Supplementary Services: Completion of Calls to Busy Subscribers - Series I: Integrated Services Digital Network; Service Capabilities - Supplementary Services in ISDN Study Group 1; 29 pp