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 invention of the keypad is attributed to
John E. Karlin, an industrial psychologist at
Bell Labs. 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. Most keypads have a
star key or
asterisk key on the bottom left and a
hash key on the bottom right.