DTMF, or dual tone multi-frequency, is the signal to the carrier you produce when you press a cell phone's touch keys. Each of the 12 DTMF signals has two tones. DTMF has generally replaced pulse dialing.
Every time you contact a company's automated system, the selections you make send DTMF tones for the company's computer systems to interpret. Voice mail, help desks and telephone banking are among the many automated systems that respond to DTMF signals.
DTMF is faster than pulse because pulse must send multiple signals for each number, while DTMF only needs to send one. DTMF is the standard for telephone companies all over the world.
Future of DTMF
As of December 2010, some companies have begun to replace DTMF with speech recognition technology, which eliminates the need to send keypad signals.