Links to useful pages and sites with technical and regulatory reference information.
World Tone Database — frequencies and cadence for telephone signaling tones throughout the world
This Is A Recording — listing of tones used around the world
PDF of ITU-T E.180 — Various tones used in national networks according to ITU-T Recommendation E.180, updated 2010.05.01
TGML: complete listing of capabilities and syntax of Tone Generation Markup Language