If you are like me a happy owner of any sippura (or now linksys spa) ata device and you are not living in US, then configuring the regional part of the device can be complicated. Especially the "Call Progress Tones" part.

First you have to know that the real important part is the following tones:

  • Dial Tone
  • Second Dial Tone
  • Outside Dial Tone
  • Prompt Tone
  • Busy Tone
  • Reorder Tone
  • Off Hook Warning Tone
  • Ring Back Tone

All this tones use a rule with the following syntax:

 freq1@db_level1,freq2@db_level2,...,freqn@db_leveln;
 num_seconds(frequency_sequence1,frequency_sequence2,...,frequency_sequencen)

With frequency_sequence with this syntax: num_seconds_on/num_seconds_off/frequencies

With this explainations 480@-19,620@-19;10(.5/.5/1+2) is quite simple to understand it is a signal of two frequencies :
480Hz and 620Hz both at -19dB during 10 seconds both frequencies (due to 1+2) will be played with this rhythm: half of second (.5) on and half of second off.

This more complicated one: 985@-16,1371@-16,1777@-16;*(.380/0/1,.274/0/2,.380/0/3,0/4/0) consists of 3 frequencies:
985Hz, 1371Hz and 1777Hz all at -16dB they will played forever (until status change for instance ...) with the following rhythm: 985Hz during 0,380 seconds then 1371Hz during 0,274 seconds then 1777Hz for 0,380 and finally no tone during 4 seconds.

If you are searching for the frequency for your country indications.conf from asterisk is your friend.