A telephone keypad is a keypad that appears on a "Touch Tone" telephone. It was standardised when the dual-tone multi-frequency system in the new push-button telephone was introduced in the 1960s, which gradually replaced the rotary dial. The contemporary keypad is laid out in a 4×3 grid, although the original DTMF system in the new keypad had an additional column for four now-defunct menu selector keys.
Read more about Telephone Keypad: Key Frequency, Letter Mapping, Illumination
Famous quotes containing the word telephone:
“The telephone gives us the happiness of being together yet safely apart.”
—Mason Cooley (b. 1927)