DTMF Controlled Car
What is DTMF? Dual-tone multi-frequency signaling (DTMF) is used for telecommunication signaling over analog telephone lines in the voice-frequency band between telephone handsets and other communications devices and the switching center . The version of DTMF that is used in push-button telephones for tone dialing is known as Touch-Tone KEYPAD The DTMF keypad is laid out in a 4×4 matrix, with each row representing a low frequency, and each column representing a high frequency. Pressing a single key (such as '1' ) will send a sinusoidal tone for each of the two frequencies (697 and 1209 hertz (Hz)). The original keypads had levers inside, so each button activated two contacts. The multiple tones are the reason for calling the system multifrequency. These tones are then decoded by the switching center to determine which key was pressed.
DTMF keypad frequencies (with sound clips)
1209 Hz 1336 Hz 1477 Hz 1633 Hz
697 Hz 1 2