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Sounds and Phone Numbers

What do Phone Numbers Sound Like?

Touch tone dialing uses a series of sounds to convey the phone number to the telephone network. These sounds are called DTMF tones and consist of two pure tones. The sounds are sent to the phone company the same way the phone conversation would be. In theory, you should be able to dial by whisteling or singing but in practice that turns out to be impossible since the frequency pairs that make up touch tone numbers are such that they cannot be generated by a single resonating body. What that means is that it takes two people to wistle a DTMF tone.

You can, however, dial a number by using an electronic gadget with a little built-in speaker which plays these tones directly into the mouthpiece of your telephone handset. Of course, the easy way to dial using touch tone is to use the keys on your phone key pad.

A touch tone phone The circuit that generates the touch tones
The Inner Life of a 1980's Telephone

Telephones, computer modems, and fax machines contain electronic circuitry which can generate these tones and send them directly up the wire to the phone company. DTMF tones can also be generated on a computer by having a program write out a data file (in one of many sound data file formats) containing the DTMF tone. You are welcome to use our computer over the web to generate sound files containing your favourite phone number.

Tone Dialing vs. Pulse Dialing

There are two commonly used protocols by which the telephone signals to the telephone network what number to dial. The older one is called "pulse dialing", and the newer one "touch tone dialing" or "tone dialing".

When using pulse dialing, each digit dialed is converted into a series of "pulses", where the number of pulses correspond to the number dialed. Each "pulse" is equivalent to the phone going "on-hook" (like hanging up the phone) for a brief moment and then "off-hook" again. The pulses can be heard as loud clicking sounds.

Pulse dialing is being phased out in most parts of the world and is being replaced by tone dialing. The developed world now almost exclusively uses touch tone dialing. Some telcos now charge an extra monthly fee to users of pulse dial telephones.

Sounds As Phone Number Mnemonics

While it is hard to use the sounds as a tool to help you remember a phone number, many people can distinguish phone numbers by sound. Even without training, you may realize you have mis-dialed a phone number on a touch tone key pad or on a rotary dial even before you finish dialing it because it did not "sound" right.

Last updated Tuesday December 11 2012
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