FOR the past half century, much of North America has used the three-digit area code. The codes were easy to pick out. (The middle number always had a ``0'' or ``1.'') So the system grew and flourished.
And now it has run out of room. The squeeze was expected. People keep adding lines for faxes and computers, regular phones, and newer gizmos like pagers and cellular telephones.
In January, the North American Numbering Plan Administration put in place the last regular area code - 610 - for the suburbs of Philadelphia. ``We're essentially out of traditional area codes,'' says Garry Benoit, manager of the Numbering Plan Administration.
So the industry, with the Federal Communications Commission's blessing, has come up with a numbering system that will extend from the United States to Canada to Puerto Rico to several Caribbean nations. (Mexico is not part of the plan.)
The new area codes will no longer have their middle numbers restricted to ``0'' or ``1.'' Instead, they'll look like the first three digits of any local phone number. They take effect next January, starting with Alabama, which will have a new 334 area code, and Washington State, which will convert some of its customers in the 206 service area to a new 360 code.
Such changes are sending shock waves through an industry accustomed to consistency. ``The change has enormous impact,'' Mr. Benoit says.
Most users will see at least a subtle change. Because a new area code will look like a local phone exchange, the ``1'' dialed ahead will become all-important. The ``1'' will be the only way for switching equipment to tell that it must wait for 10 more digits before completing the call. This move will force another change.
Currently, callers who want to make a long-distance call from, say, Pittsburgh to Grove City, Pa., dial a ``1'' and then a seven-digit number. Both cities lie within the 412 area code. The new long-distance plan is forcing states to drop this 1-plus-seven scheme for calls within the same area code. Pennsylvania and other large, populous states are simply dropping the ``1.'' More rural states will force users to dial ``1,'' plus their own area code, plus the number.
Remembering which state uses which method is an inconvenience for residential customers. For businesses, it could spell catastrophe. That's because many companies use their own telephone-switching equipment - called a PBX or private branch exchange. Typically, these PBXs have been programmed to recognize long-distance calls by the ``0'' or ``1'' middle digit. The new system could wreak havoc.
It is ``a significant problem,'' says Mary Bradshaw, director of industry relations at the North American Telecommunications Association (NATA) in Washington, D.C. ``The problem may not be as large in terms of the financial commitment.... [But] there can be a lot of uncertainty on the users' part.''
Until January, PBX manufacturers were not even told which states would be using which system to replace the 1-plus-seven scheme, she says. Now, they are working to let their customers know how to deal with the problem.
It won't be easy. By one estimate, the US alone has some 37 million PBX lines in use. Virtually all of them need upgrading, NATA warns. By some estimates, the total cost of US conversion could reach $1 billion.
To further complicate matters, some large cities use multiple area codes. A New Yorker in the 212 area code can dial a 718 Bronx number but not get charged for a long-distance call. Two years from now, Los Angeles will add a new 562 area code. But instead of being geographically based, it will be added to new numbers all over the metropolitan area. That means that two friends on the same floor of an apartment building may have to dial ``1'' plus 10 digits to call each other.
Despite the cost and confusion, the industry has little choice.
It could follow the lead of France and Japan and adopt eight-digit local numbers, but industry leaders say that would cause even more confusion. New phone numbers are needed quickly. The Numbering Plan Administration forecasts that 18 area codes will run out of space before the year 2000 if nothing is done.
At least the new system will be around for awhile. ``It should last another 30 years,'' Benoit says. ``But, you know, it could be 50, or it could be less than 30.''