Old telephone with rotary dial

Human Factors Engineering Studies of the Design and Use of Pushbutton Telephone Sets

In a recent post on Data Genetics blog, the author writes: “Have you ever thought “Why are the numbers on a telephone keypad arranged the way they are? Why are they arranged in a 3×3 grid with the zero below? How did this layout become a standard? Why is this layout subtly different to the way the numbers are arranged on a calculator or numeric keypad? What other layouts were considered? The answers to these questions can be found in a fascinating piece of research performed by AT&T in 1960.


The article was entitled: Human Factors Engineering Studies of the Design and Use of Pushbutton Telephone Sets […] This classical piece of research covers four aspects of the keypad design: Key arrangement, Force displacement characteristics, Button top design, and Central office factors. The outcome of this research project and testing is the keypad we know today. In my blog posting I’m going to summarize just the results the key arrangements. For details of the other criteria and decisions refer to the article.”


The abstract – From the user’s point of view, what are the desirable characteristics of pushbuttons for use in 500-type telephone sets? The studies reported bear on this question and also on questions of how people process information when keying telephone numbers. Four categories of design features were studied: key arrangement, force-displacement characteristics, button-top design and central office factors. The results indicate that considerable latitude exists for key set design in terms of user performance; however, the preference judgments are more selective. The studies also showed that the manner in which the person acquired and keyed the telephone number influenced performance appreciably.

Download the original paper.