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:
“A woman spent all Christmas Day in a telephone box without ringing anyone. If someone comes to phone, she leaves the box, then resumes her place afterwards. No one calls her either, but from a window in the street, someone watched her all day, no doubt since they had nothing better to do. The Christmas syndrome.”
—Jean Baudrillard (b. 1929)