Telephone Keypad - The Facts & Origin of Telephone Keypad

What Is Telephone Keypad?

Telephone Keypad is known as a keypad which used to and still appears on touch tone telephone. In 1960's when the dual-tone multi-frequency system in a new technology named 'push button telephone' was introduced, the telephone keypad was embedded in them. The telephone keypad was made a standardized part of the push button telephone.

Although the contemporary telephone keypad is laid out in a 4×3 grid, the original DTMF system in the new telephone keypad had an additional column for four now-defunct menu selector keys.
a telephone keypad image

What Are the Tones in Telephone Keypad?

When a button on the telephone keypad is pressed to dial a number, We hear a different tone for different buttons on the keypad. Many may wonder whats the use or how it is produced, The answer to the question is quoted below:
Pressing a single key on the telephone keypad will produce a pitch consisting of two simultaneous pure tone sinusoidal frequencies. The row in which the key appears determines the low frequency, and the column determines the high frequency. For example, pressing the '1' key will result in a sound composed of both a 697 and a 1209 hertz (Hz) tone.
Given below is a chart to make you understand the frequencies of different numbers on the keypad.
telephone keypad - tone frequencies in telephone keypads
One interesting fact about the telephone keypad is that the '#' Key has different versions of names according to one's personal preferences or nationality,

The following Are a Few Names for the # Sign:
  • Hash
  • Pound
  • Number
similarly the '*' key is also called the Star Key or the Asterisk.

Did You Know?

In UK (British) you can order an Alarm Clock @ Morning 7.30AM from the British Telecom Telephone Exchange by dialing *55*0730# on your telephone keypad.

With the recent versions of the Telephone Keypad, You can see the alpha numeric characters on the telephone keypad,

They are arranged as follows

0 = none OR Operator
1 = none OR QZ
2 = ABC
3 = DEF
4 = GHI
5 = JKL
6 = MNO
7 = PQRS
8 = TUV
9 = WXYZ

Telephone Keypad Tricks

Telephone Keypad Tricks - How to Detach Telephone Keypad Easily

Following are the steps which you can implement to quickly and easily detach your telephone keypad.
  1. Switch OFF your phone.
  2. Place it upside down.
  3. Remove the battery after taking off the back cover.
  4. Remove all the screws from the back panel with the help of a screw driver that has cross heads.
  5. Keep removing all the screws until the panel is completely loosened.
  6. Take out the front panel and the keypad cover.
  7. After removing the keypad cover prick the keypad to loosen the grip.
  8. Detach the keypad cable.
  9. Remove the keypad.
  10. That is it Done! :)
Letter Mappings On Telephone Keypad

When designing or selecting a new phone, publishing or using phonewords, one should be aware that there have been multiple standards for the mapping of letters to numbers on telephone telephone keypad over the years.

The system used in the UK was different from that used in France which was different from the US etc. The use of alphanumeric codes for exchanges was abandoned in Europe when international direct dialling was introduced in the 1960's, because dialling WHI 1212 on a French phone would get different numbers to dialling it on a British phone.

At the same time letters were no longer put on the dials of new telephones.

Letters did not re-appear on phones in Europe until the introduction of mobile phones, and the layout followed the new ITU E.161 / ISO 9995-8.

The telephone keypad pictured above is mapped according to the current international standard. The standard ITU E.161 introduced in the mid-1990s, and that should be the layout used for any new devices.

Since many newer smartphones have full keyboards instead of the traditional telephone telephone keypad, the user must execute additional steps to dial a number containing convenience letters. On certain BlackBerry devices, a user can press the Alt key, followed by the desired letter, and the device will generate the appropriate DTMF tone.

The first telephony application that did not deploy a dial pad is Blink. As computers benefit of a full keyboard, the developers felt that it was more natural to allow typing DTMF tones by using the computer keyboard while in a middle of an audio session without having to present the end-user an explicit dial-pad graphical user interface.

Those were some of the real facts on telephone keypads.