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Appendix
Acoustic signals
Steady tone
Internal dial tone
Confirmation tone
Busy tone
Ring tone
External dial tone
Error beep/range warning
Beep
Beep
Beep
Pause
Beep
Pause
0.2 s/0.3 s beep/pause, sequence repeated after 0.5-s pause
0.8 s
2 s
0.5 s beep/pause
0,8 s
4 x 0.1 s beep/pause
...
...
Call waiting tone
0.1 s
0.1 s
10 s
Pause