The rectangular design of the keypad, the shape of its buttons and the position of the numbers — with “1-2-3” on the top row instead of the bottom, as on a calculator — all sprang from empirical research conducted or overseen by Mr. Karlin. .
.... Among the issues Mr. Karlin examined as the head of Bell Labs’ Human Factors Engineering department — the first department of its kind at an American company — were the optimal length for a phone cord (a study that involved gentle, successful sabotage) and the means by which rotary calls could be made efficiently after the numbers were moved from inside the finger holes, where they had nestled companionably for years, to the rim outside the dial.
..... An early experiment involved the telephone cord. In the postwar years, the copper used inside the cords remained scarce. Telephone company executives wondered whether the standard cord, then about three feet long, might be shortened. Mr. Karlin’s staff stole into colleagues’ offices every three days and covertly shortened their phone cords, an inch at time. No one noticed, they found, until the cords had lost an entire foot.
... From then on, phones came with shorter cords. ... Mr. Karlin also introduced the white dot inside each finger hole that was a fixture of rotary phones in later years. After the phone was redesigned at midcentury, with the letters and numbers moved outside the finger holes, users, to AT&T’s bewilderment, could no longer dial as quickly.
With blank space at the center of the holes, Mr. Karlin found, callers no longer had a target at which to aim their fingers. The dot restored the speed.
Mr. Karlin’s biggest challenge was almost certainly the advent of the push-button phone, officially introduced on Nov. 18, 1963, in two Pennsylvania communities, Carnegie and Greensburg.
In 1946, a Bell Labs engineer, Rudolph F. Mallina, had patented an early model, with buttons arranged in two horizontal rows: 1 through 5 on top, 6 through 0 below. It was never marketed.
By the late 1950s, when touch-tone dialing — much faster than rotary — seemed an inevitability, Mr. Karlin’s group began to study what form the phone of the future should take. Keypad configurations examined included Mr. Mallina’s, one with buttons in a circle, another with buttons in an arc, and a rectangular pad.
The victorious design, based on the group’s studies of speed, accuracy and users’ own preferences, used keys half an inch square. The keypad itself was rectangular, comprising 10 keys: a 3-by-3 grid spanning 1 through 9, plus zero, centered below. Today’s omnipresent 12-button keypad, with star and pound keys flanking the zero, grew directly from this model.
Putting “1-2-3” on the pad’s top row instead of the bottom (the configuration used, then as now, on adding machines and calculators) was also born of Mr. Karlin’s group: they found it made for more accurate dialing.Comment: More: Dual-tone multi-frequency signaling and 951 Western Electric model 500 telephone