From rotary to Siri: How the phone numbering system came and went

© John Karlin/ Alcatel-Lucent

The recent death of John E Karlin of Bell Labs, the father of the push-button phone and other innovations, has sparked a lot of reminiscing about land line phones. According to the New York Times, Karlin was also "the most hated man in America" for killing the named exchanges (like Butterfield 8). However the story of how our phone numbers got to be the way they are is a much longer and more interesting one.

In 1992, Brian Hayes wrote a wonderful article that I have always remembered on the subject, in the late and lamented magazine The Sciences, titled The Numbering Crisis in World Zone 1. (PDF Here)

Even the very beginning of the story is interesting, if not quite believable:

According to legend, Almon B. Strowger was a Kansas City undertaker who found he was losing business to a rival. Potential customers would telephone Strowger but "mistakenly" be connected to his competitor. Strowger noted that the competitor's wife was the switchboard operator for the local telephone system. His revenge was to invent a device that would eventually displace operators almost everywhere.

The switch worked in a linear fashion, so you couldn't have one person with a number 76 and another 7644; it needed all four digits to work. It couldn't start with 0, because that would connect you with the operator before you were finished. They didn't start with 1 either; it was used for internal switching. Needless to say, they soon ran out of numbers and went to seven digit dialing. There was a lot of concern that people couldn't keep track of so many digits, so they gave names to the exchanges, hence Elizabeth Taylor's famous BUtterfield 8 and my grandmother's EMpire 3.

In 1950 it got really interesting, with the introduction of area codes. The designers wanted to minimize the number of numbers people had to dial, so all the area codes were set up to have 1 or 0 as the second number. The switches were set up so that if first number dialed was a 0 then it went to operator. If the second digit was 1 or 0, then it was an area code. If the second number was another number, then it knew it was a local rather than long distance number. That's how it was going to distinguish between 7 and 10 digit numbers.

The lowest numbers went to the largest cities; that's why New York got 212, the lowest possible area code and fastest to dial on a rotary phone. Nobody wanted 0 in the middle. (More on 212 at Core77)

AT&T/Screen capture

However that required some kind of electronic buffer to hold the number until it could read the second digit, and a lot of switches couldn't do that yet. So as a temporary cludge, they added a requirement that you dial 1 for long distance. It wasn't supposed to last. Hayes writes:

The planners of the telephone network had taken pains to design area codes that could be distinguished automatically from central-office codes, but 1+ dialing made the internal distinction redundant. For a time, a faction within the Bell System hoped and expected that 1+ dialingwould eventually disappear. In their view the coding was an elegant and parsimonious scheme that cleverly exploited all the peculiarities of the existing switching network to extract the maximum information from the minimum number of digits. In contrast, 1+ dialing was a crude and wasteful patch that should be dispensed with as soon as the last step-by-step switching plant was scrapped. But the patch is still with us, and it has patches of its own now.

Eventually, and long after Hayes wrote this article, the phone companies gave up on the 0 and 1 in the middle of the area code; the computer buffers could remember the whole sequence and would know whether it was a 7, 10 or 11 digit number and route it accordingly.

I love Hayes' last paragraph (remember, this was written in 1992), where he predicts the future:

Telephone numbers may eventually become obscure internal codes that the general public has no need to know. Already many telephones come with speed-dialing buttons so that you record frequently called numbers (and thereafter forget them). There are also pocket-size dialers you hold up to the mouthpiece of a telephone. If you wish, the telephone company will store your list of favorite numbers, so that you can dial them with a one- or two-digit code. Such strategies for insulating the customer from the number itself will become more prevalent as numbers grow longer and harder to remember. I can imagine a kind of user interface that might ultimately evolve. In a couple of decades, perhaps, the telephone will have no dial at all. You will simply pick up the receiver and say, "Jenny, get me Mrs. Wilson, please. Thank you, dear."

Substitute Siri for Jenny and that's exactly what we have.

Tags: Electronics | Technology | Wayback Machine

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