A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

Why are those red balloon things on overhead wires? How are area codes assigned?

July 15, 1988

Dear Cecil:

The questions you deal with in your column are usually pretty cosmic, but maybe as a change of pace you wouldn't mind taking a whack at the following shallow topics: (1) What are those red or orange balloon things you see on high-voltage utility wires when you're driving out in the country? I've heard several theories, but none seems to hold up under critical examination. (2) Is there any rhyme or reason to the assignment of area codes? Why aren't numerically sequential codes given to geographically adjacent areas? When I call Mom in area code 414 (eastern Wisconsin) but get San Francisco (415), it seems like a plot to separate me from more of my money.

Cecil replies:

Johnny, Johnny, Johnny. (Kinda Garboesque, ain't it?) The telephone company is your friend. One of the reasons area codes are assigned the way they are is precisely to prevent you from dialing the wrong code by mistake. But let's take your questions in order.

(1) The "balloon things" are aircraft warning markers intended to prevent some joker in a Piper Cub from clotheslining himself. You see them near airports with a lot of general aviation traffic —  i.e., low-flying small planes — or else in areas where they do crop dusting. Typically the markers are fiberglass spheres tricked out in some high-visibility color, but occasionally you see other designs as well. They've definitely inspired their share of carrot-brained theorizing. I knew a guy who said the purpose of the balloons was to "scare away the birds." Tragic evidence of the impact of the thinning ozone layer.

(2) The assignment of area codes may seem random or even malevolent to you, John, but this merely reflects your troubled inner being. Actually it's pretty sensible. The North American Numbering Plan, of which the area codes are a part, was worked out in the late 1940s to ensure standardized numbering nationwide, helping to make direct-dial long distance possible. (Prior to that time you had to go through an operator.)

On the rotary-dial phones then in use, dialing a nine took a lot longer than dialing a one, which tied up expensive switching equipment. So AT&T assigned "low dial pull" numbers to the markets with the most telephones and thus presumably the highest number of incoming long-distance calls. New York got 212, Chicago 312, LA 213, Detroit 313, Dallas 214, and so on.

Some area codes aren't so easy to explain. Boston got 617 while comparatively rural western Massachusetts got 413; Washington, D.C., got 202. (Zero, remember, has the highest dial-pull of all.) Whether these anomalies represented some smoldering vendetta against the eastern seaboard we may never know; the people responsible have long since retired.

The issue of dial pulls became academic with the introduction of Touch-Tone phones in the early 1960s. Since then the guiding principle behind the assignment of new area codes has been to make the new number as different as possible from the adjacent old ones in order to avoid confusion. That's why the split of New York's 212 produced 718, LA's 213 begat 818, and Chicago's 312 was joined by 708. The drawback of this approach is that when you do make a mistake it's a lulu, giving you San Francisco, for example, when you were trying to dial Milwaukee. But the phone company will readily delete such goofs from your bill.

As far as Ma Bell was concerned, the real problem with assigning area codes was that it began running out of numbers to assign. Originally the switching system required that the middle digit in each code be a one or a zero, which meant there were only 152 numbers available. By the early 1990s, all but a handful of these had been spoken for. To get around this limitation, phone companies around the country began implementing "Dial-1" service, which required you to dial 1 at the start of any direct-dial long-distance call. This permitted the use of additional digits in the middle position, giving us a total of 792 potential codes. Just in time, what with the proliferation of area codes required by the growing use of cell phones, faxes, and modems. Phone company geniuses used to think 792 codes would hold us forevermore; now, who knows?

Area codes: A wrong number

Dear Cecil:

Unless I'm missing something, you slipped a bit in your discussion of area codes. You said "the switching system requires that the middle digit in each code be a 1 or a 0, which means there are only 152 numbers available." If this in fact were the only constraint, there would actually be 200 possible combinations (10 x 2 x 10). But I believe there's a further constraint: the first and third digits may not be 1 or 0. This leaves eight digits available for positions one and three, or 8 x 2 x 8 = 128 possible area code combinations. So where does 152 come from? And if in the future the constraint on the middle digit is eliminated, how do you figure there will be 792 potential codes?

Cecil replies:

You want details, I'll give you details. There are eight potential digits in the first position; zero and one are ineligible. There are two potential digits in the second position and ten in the third. 8 x 2 x 10 = 160. Codes 211 through 911, eight codes in all, were reserved for special uses, e.g., 411, directory assistance. This leaves 152. (Most of the "-10" codes, such as 210, have not been assigned, but they could be. The international long-distance access code, 011, is not considered part of the area code universe by definition.) When the middle digit constraint is eliminated, the number of potential codes will be 8 x 10 x 10 = 800 minus the eight reserved codes, or 792.

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