• CCITT Rec. U.40 (11/1988) – REACTIONS BY AUTOMATIC TERMINALS CONNECTED TO THE TELEX NETWORK IN THE EVENT OF INEFFECTIVE CALL ATTEMPTS OR SIGNALLING INCIDENTS
  • 1 Ineffective outgoing call
    • 1.1 Non-return of the call-confirmation and/or proceed-to-select signal(s)
    • 1.2 Slow or incomplete selection
    • 1.3 No response after selection
    • 1.4 Ineffective attempts followed by service signals
    • 1.5 Ineffective calls characterized by a clearing signal without a preceding service signal
    • 1.6 Reception of an answerback
    • 1.7 Simultaneous calls
  • 2 Ineffective incoming calls
    • 2.1 False calls
  • 3 Incidents following call set-up
    • 3.1 Idle circuit without clearing signal
    • 3.2 No clear-confirmation