Years ago, we found the info below and created our own little phone sound library (click here to download our low-res Shareware library). Each tone is made up of two separate tones according the matrix below.

1209 1336 1477 1633
697
1
2
3
A
770
4
5
6
B
852
7
8
9
C
941
*
0
#
D

Thus, the number one is a combination of two tones, at 697Hz and 1209Hz. # is 941Hz and 1477Hz.

Recently, we did some fun work for AT&T's web site in Shockwave We found good results by using 0.5 second samples at 8 bit, 11Khz (under 6k per tone). Use equal amplitudes of each tone and mix to a single channel. It won't take you long to create what you need. For non-Shockwave projects you might want to create higher fidelity sounds (i.e., 16-bit 22Hz).

Other useful tones are:
  Dial tone 350 and 440
  Ringing 440 and 480. Normal is 2 seconds on, 4 second off, PBX is 1.5 second on, 4.5 seconds off
  Busy 480 and 620, Normal 1/2 second, on 1/2 second off, congestion 0.2 on, 0.3 off, reorder 3 on, 2 off.

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