Appendix
Acoustic signals
Internal dial tone
3 x 0.2s tone and 0.3s pause, sequence repeated after 0.5s pause.
External dial tone
Steady tone
Ringing tone
Tone |
| Pause |
| Tone |
| Pause |
| Tone |
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0.8s 2s
Busy tone
0.5s 0.5s
Acknowledgement tone
Tone
0.8s
Error tone/range tone
4x0.1s
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