Chamblee54

Why Telephone Keypads Are Different From Computer Keypads

Posted in Library of Congress, Undogegorized by chamblee54 on February 5, 2019


It is a question for the ages…why do telephones have 123 on the top row of the keypad, while computers have 789? The best answer is , we don’t know.

Calculator/computer keypads were an improvement on cash registers. These devices had a matrix of buttons, with the 9 row on top. The row at the far right had single digits, and the row next to them had digits ending in one zero. To ring up a sale for $1.95, you had to push 100, 90, and 5. This evolved into the adding machine configuration of three rows of three buttons, with 0 on the bottom row and 789 on the top row.

When we got started, the telephone used a dial. 1 was at the top, and 0 was at the bottom. The early phone systems used letters as part of the phone number. The first three letters of the seven digit code were two letters and five numbers. (This is what PG remembers from childhood. It may have been different before then).

The two letters referred to an exchange, or part of town where the number was located. The two letters referred to a word. An example would be PG’s grandmother. Her number was TR2 2345. The TR stood for Trinity. Many numbers in midtown Atlanta still start with 87.

In the sixties, ma bell started to develop a keypad to use for what were then called push button phones. In a break with the adding machine tradition, the numbers 123 went on the top row. There are a few ideas why this is, but nothing is certain.

In the early days, the phone switching equipment was not as fast as today. Some thought that by switching the numbers to the top of the keypad, people would have to slow down a bit to “dial” the number. This answer does not make sense to those of us who have grown up with these keypads, and who learned to punch in numbers fast, no matter what system is used. (Anyone using a rotary phone, after getting used to touch tone, is shocked at how slow it is.)

Another concept is the phone company wanting to model the new keypad after the dial phones. This would mean putting the 1 at the top, and 0 at the bottom. Also, with the letters assigned to each number, it would make a lot more sense to have 123/abc def ghi on the top row.

It was suggested that the calculator keypad was patented in the 789-on-top format. Western Electric did not want to pay royalties on this important piece of equipment, so it designed another one. There is also the thought that the calculator was on a desk shelf, where the lower numbers should be at the bottom of the keypad. At the same time, the telephone was on the lower part of the desk, and having 123 on top would be easier to use.

This is a repost. This comment was left on facebook, after the first post.

I won’t pretend to know exactly their reasons, but I will say that I can see some logic in doing it this way. In a numerical context (calculator/computer), you’d want zero next to one, which is where it is in the number sequence. However on… a telephone, 0 has a special meaning: call the operator (at least, it used to mean this).

The guys at Bell Labs took this into consideration when they implemented the “touch tone” or DTMF dialing system. Old style pulse dialing was annoying because it would literally send a pulse for each number (two pulses for two, nine pulses for nine, etc). I meant larger numbers took longer. To change this, and also in anticipation of the fact that eventually phones would be connected to computers, they instead put all the numbers on a grid with each row and column assigned a unique frequency. Each key on the pad combined the two frequencies to produce a tone. In order to accommodate ten numbers, you need a grid of at least 4X3, which they actually increased to 4×4 because they wanted some additional tones (A-D) for extra network functionality.

This is a repost. Pictures are from The Library of Congress.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: