Dual Tone Multiple Frequency (DTMF) is a signaling method developed by Bell Labs for sending telephone dialing information over the same analog, voice-quality phones lines that carry voice.
Each digit is encoded as the sum of two sine wave bursts, of different frequencies. The two-tone method was chosen because it can be reliably distinguished from voice and normal phone conversations are highly unlikely to falsely trigger the DTMF receiver.
DTMF was the basis for "TouchTone" (a former trademark of AT&T), the pushbutton system that replaced mechanical rotary dial telephones.
- Dual Tone Multiple Frequency
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