INTRODUCTION to DTMF
DTMF stands for Dual Tone Multiple Frequency; it is used to send information through phone lines to and from your local exchange.
Dual Tone Multiple Frequency (DTMF) is also known as Touch-tone, Tone Dialling, VF Signaling and MF Dialling.
Each DTMF tone consists of two simultaneous tones (one from the high group and one from the low group), which are used to indicate which number or symbol you press on your telephone's keypad. For example if you press number 5 on your telephone's keypad, the tone you will hear is 1336hz and 770hz played simultaneously.
DTMF is an extremely reliable signaling method used by all telecommunications companies to receive information from their customers. Whenever a number is dialled on a home phone, office phone, public or private payphone, DTMF is decoded and used by certain equipment inside that particular area's local exchange to call the number you have dialled.
Dual Tone Multiple Frequency is the basis of voice communications control. Modern telephone circuits use DTMF to dial numbers, configure telephone exchanges (switchboards) from remote locations, program certain equipment and so on.