ITU-T X.60-1989 Common Channel Signalling for Circuit Switched Data Applications - Data Communication Networks - Transmission, Signalling and Switching, Network Aspects, Maintenance and Administrative Arrangements (Study Group VII) 2 pp
that public networks providing circuit-switched data transmission services are being established in various countries
ITU-T X.60-1989 history
1989ITU-T X.60-1989 Common Channel Signalling for Circuit Switched Data Applications - Data Communication Networks - Transmission, Signalling and Switching, Network Aspects, Maintenance and Administrative Arrangements (Study Group VII) 2 pp