DTMF Dual-Tone-Multi-Frequency aka Touch Tones

• DTMF Touch-tone Generator and Decoder
• Generating DTMF tones using soundcard
• Microchip PIC specific DTMF
• Ubicom SX specific DTMF (includes Ubicom Application Note 41: "DTMF Detection and Generation", a pretty detailed description).

Plain Old Telephone Service@

See also

• http://www.infobahnos.com/~benh/text/dtmf.htm DTMF FAQ
• http://mondo-technology.com/qdft.html How to decode DTMF (or detect other frequencies) in a computer without complex math.

Questions:

• anant_k31@yahoo.com asks:

  I am a fresh graduate working for a telecom company. Here i have a doubt on DTMF. Kindly clarify my doubt. Why we need dual tone instead of single. Any way we are going to pass a single frequency from DTMF filter after mixing the two generated frequences. Instead of doing that we can have a single frequency with high quality filter. Regards Ananth