ITU-T F.68-1988 Establishment of the Automatic Intercontinental Telex Network - Telegraph and Mobile Services Operations and Quality of Service (Study Group I) 6 pp
The circuits to be used when the primary routes are congested. The secondary route(s)
may pass through the same countries as the primary routes or through different countries. In manual and semi-automatic operation, secondary routes may also be used when
ITU-T F.68-1988 history
1988ITU-T F.68-1988 Establishment of the Automatic Intercontinental Telex Network - Telegraph and Mobile Services Operations and Quality of Service (Study Group I) 6 pp