Dual-tone multi-frequency facts for kids
Dual-tone multi-frequency or DTMF is the group of special sounds a telephone makes when you push the buttons. Each number button makes a different sound. Telephone company equipment hears each sound and turns it back into a number. When all the numbers in a phone number are pushed the telephone company equipment will make the other person's telephone play a loud sound so they can answer their telephone and talk to you.
Telephones also have a star (*) button and a pound (#) button. These buttons also make different DTMF sounds. These buttons can be used for other things like 'go' or 'do over'. But they are not part of the phone number.
A few telephones have the letter buttons A B C and D. They also make different DTMF sounds.
Pushing the number buttons is called dialing the telephone. When a telephone makes a loud sound for you to answer, it is called ringing.
Images for kids
-
The keypads on telephones for the Autovon systems used all 16 DTMF signals. The red keys in the fourth column produce the A, B, C, and D DTMF events. In this case the letters indicate the precedence (urgency) of the call; (from lowest (at the bottom) to highest; Priority, Immediate, Flash or Flash Override
-
Combination of 1209 Hz and 697 Hz sine waves, representing DTMF "1"
-
Two CMD CM8870CSI DTMF Receivers
See also
In Spanish: Marcación por tonos para niños
