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A Unified Architecture for Telephone Numbers

In the area consisting of Canada, the United States, and the Carribean (excluding Cuba), which area is that having Country Code 1, a subtle change in telephone numbering took place recently, which caused inconvenience in dialing for many people.

In Australia and Great Britain, the need for more telephone numbers resulted in telephone numbers being lengthened by a digit in those countries.

A change of this nature involves large expenses to businesses, in changing forms and computer databases which handle telephone numbers. Such a change would have caused a very large expense in North America, comparable to that associated with the "Year 2000" problems involving the representation of dates.

It was possible to avoid this in North America by altering a characteristic of telephone numbers as they had existed there.

A popular song bore the title "PEnnsylvania 6-5000". This is how telephone numbers were once represented; the first three digits, indicating a telephone exchange, were indicated by a name and a single digit, such as GLendale 2- (representing 452-) or MUtual 6- (representing 686-). Thus, the digits 0 and 1, which were not accompanied by letters on the telephone dial, the layout of which is:

    ABC DEF GHI JKL MNO PRS TUV WXY OPERATOR
 1   2   3   4   5   6   7   8   9   0

could not be either of the first two digits of an exchange.

Dialing 0 put you in touch with the operator, and dialing 1 begins direct long-distance dialing. Any other digit can be the beginning of a telephone number.

If the second digit was a 1 or a 0, that meant that you were dialing an area code. Three digit special service numbers, such as 411 for information, 611 for service, or 911 for emergencies, as well as the 800 code for toll-free numbers and the 900 code for special charge-based services, also belonged to this class. (Before the advent of direct distance dialing, toll-free numbers belonged to exchanges which began with ZEnith; as the letter Z is not on the telephone dial, this reminded people they needed to contact the operator to reach them.)

This meant that telephone numbers had the prefix property: since three-digit exchanges and three-digit area codes were distinct, one could make a long-distance call within one's own area code without dialing the area code.

Recently, this was abolished: now, exchange codes and area codes are no longer distinct. This made some additional exchanges, and many new area codes, available, thus addressing the need for more telephone numbers, while keeping the length of a full North American number, including area code, constant at ten digits.

Having five times as many area codes does seem like it should be enough to last for many years to come. However, one unfortunate result of it is that people in some larger cities have had to dial ten digits for every local call they make.

I would like to suggest an alternative approach to the problem, which would preserve the brevity of telephone numbers as seen by most ordinary users of the system, although it would mean that business concerns which recorded telephone numbers of people from all parts of the country would need to modify their databases.

The Proposal: Basic Level

I propose that the prefix property of the telephone numbering system within Country Code 1 be restored, in the following modified form:

Let n stand for a digit belonging to the set:

{2, 3, 4, 5, 6, 7, 8, 9}

Let m stand for a digit belonging to the set:

{2, 3, 4, 5, 6, 7, 8}

Let d stand for an arbitrary digit from 0 to 9.

Let x stand for one of the digits 0 or 1.

I propose that a seven-digit telephone number would have the form nnd-mddd. An area code would have the form n1n (not n1d: n1x would be the form of three-digit numbers, such as 411 for information) and a region code would have the form n0n. (again, not n0d: 800 is for toll-free numbers, 900 for pay services. 888- numbers would be changed to 801- numbers.)

The full form of a telephone number would be region code - area code - seven-digit number, and so one would dial only seven digits within one's own area, and only ten digits within one's own region, and thirteen digits outside one's region.

However, if a region is not subdivided into areas, dialing to that region from outside would only require ten digits; this would create no ambiguity.

One would continue to dial 0 for the operator, and 1 for direct distance dialing. I propose that 10- be made the prefix code for international calls, so that there would be no need for a timing dependency in decoding such calls, as there is in disambiguating 01- from just plain 0.

Concrete Area Code Choices

One thing that helps to make this scheme practical is that, in 1947, when the area code system was first instituted, those states and provinces which had only a single area code received an area code with a 0 in the middle, just the type of area code I am proposing to use as the higher-level code in this system.

States and provinces that started out with multiple area codes received ones which had 1 in the middle.

Using the original area code for a region which started out with only one area code, and any later assigned code with a 0 in the middle for a region with multiple codes, we can find existing codes for most places:

201 New Jersey            401 Rhode Island    601 Mississippi        801 Utah
202 Washington, D. C.     402 Nebraska        602 Arizona            802 Vermont
203 Connecticut           403 Alberta         603 New Hampshire      803 South Carolina
204 Manitoba              404 Georgia         604 British Columbia
205 Alabama               405 Oklahoma        605 South Dakota
206 Washington            406 Montana                                806 (Texas)
207 Maine                                     607 (New York)
208 Indiana                                   608 (Wisconsin)        808 Hawaii
209 (California)                                                     809 Carribean

301 Maryland              501 Arkansas        701 North Dakota       901 Tennessee
302 Delaware              502 Kentucky        702 Nevada             902 Maritimes
303 Colorado              503 Oregon          703 Virginia           903 [Mexico]
304 West Virginia         504 Louisiana       704 North Carolina
305 Florida               505 New Mexico      705 (Ontario)          905 [Mexico]
306 Saskatchewan                              706 [Mexico]
307 Wyoming               507 (Minnesota)                            907 Alaska
                          508 (Massachussets)
309 (Illinois)                                709 Newfoundland

Where the name of the area is in parentheses, the code is one introduced only for a part of the area. Idaho, Kansas, Michigan, Montana, Ohio, Pennsylvania and Quebec are areas that do not have an obvious region code assignment that can be obtained in this manner, but there are, of course, enough codes available.

408, 707 and 805 are other possibilities, in addition to 209, for California, 906 is another possibility for Wisconsin, and 609 and 908 are two codes added to New Jersey, 308 is a code added to Nebraska, 904 a code added to Florida, 606 a code added to Kentucky, 804 a code added to Virginia, and 509 a code added to Washington state.

Mexico is not part of the Country Code 1 area, but the three area codes shown for Mexico were provided to permit parts of Mexico to be reached without needing to resort to international dialing.

In this way, one could simply store the last ten digits of a phone number, and deduce the region code from the address, since every state or province would have only one region code.

The Proposal: Advanced Level

The above is another method of making many new telephone numbers available. It allows seven-digit dialing to be used wherever possible. By itself, however, it will not fully solve the problem of large cities with more than one area code, even if people can dial only seven digits to call numbers in their own part of the city.

Note that I have treated the digit 9 as special in the foregoing to a limited extent.

I also recommend the following:

That, if still more telephone numbers are needed, this be achieved by lengthening region codes and area codes to four digits by appending an additional arbitrary digit. Thus, a region code would have the form n0nd, and an area code would have the form n1nd. This would be done without lengthening the numbers like 411, as the fourth digit would be regarded as a suffix to the area code or region code. 800 and 900, on the other hand, would be suffixed.

While numbers within a single area code would be only seven digits long, subscribers within a city encompassing multiple area codes would have the option of choosing to dial local numbers in either of two alternate forms:

The basic or default form: nnd-mddd for numbers within their own area, and n1n-nnd-mddd for numbers in other areas, or

in the extended form nnd-d-mddd where the extra digit after the exchange would indicate which area was being called. This digit might be, if unambiguous, the last digit of the area code.

Furthermore, in the opposite case, where one lives in a small town, or a close-knit small neighborhood, or is in a business with a Centrex system, one could elect to dial 9 to make a call outside of one's own exchange. Since the last four digits have the form mddd, specifically, the second digit is arbitrary, one would have to dial 9-411 instead of 411 for information, and so on, in that case.

Let us suppose your telephone number is (204)(612) 555-3131 under this system. The following table shows how you would dial some other telephone numbers for the three cases:

                      Default              Extended             Local
In the same city:
411                   411                  411                  9-411
(204)(612) 555-2121   555-2121             555-2-2121           2121
(204)(612) 888-2121   888-2121             888-2-2121           9-888-2121
(204)(216) 555-2121   216-555-2121         555-6-2121           9-216-555-2121
---
Out of town (Extended Flat Rate Calling Area):
(204)(612) 777-2121   777-2121             777-2-2121           9-777-2121
(204)(516) 555-2121   516-555-2121         516-555-2121         9-516-555-2121
(607)(419) 555-2121   607-419-555-2121     607-419-555-2121     9-607-419-555-2121
---
Out of town (Long distance):
(204)(318) 555-2121   1-318-555-2121       1-318-555-2121       1-318-555-2121
(406)(412) 555-2121   1-406-412-555-2121   1-406-412-555-2121   1-406-412-555-2121
(705) 555-2121        1-705-555-2121       1-705-555-2121       1-705-555-2121

This would fulfill several goals.

Every telephone number would have a canonical form, and thus would be reachable from outside the system in a unique way. A dummy area code, for example 919, could be allowed when dialing a number in a region not subdivided into areas, so that every number would have exactly thirteen digits, thus facilitating incoming international calls.

The Default dialing system would preserve the existing appearance of the telephone system, and restore the ability to dial only seven digits in many cases.

The Extended and Local dialing systems would permit the flexibility to allow dialing numbers with the minimum number of digits: four instead of seven in smaller centers using the Local system, eight (or nine) instead of ten in larger centers for which seven digits are not adequate.

Note that I wanted to use 555-1212 in the examples above, but couldn't, as the four digit base part of a number is of the form mddd, and can't start with a 0, a 1, or a 9.

Also, if people are uncomfortable with numbers having thirteen digits in their canonical form, one could inaugurate the system with the less-frequently-used region codes having four digits each - or two digits each, since only a limited number of regions would be required initially. In the latter case, 800 numbers and the like would have to be shifted a bit, perhaps by being given area codes within the 80 region.

Condensed Storage Representation

Finally, I have not forgotten those businesses that would encounter problems with storing thirteen-digit telephone numbers on their computers. Recall that every area code now has 1 as its middle digit. Since only a limited number of region codes would be needed initially with this proposal - two region codes would restore the amount of telephone numbers that existed before the prefix property was abolished, so probably three to five regions would suffice in the beginning - one could replace the middle digit of the area code by a single digit (or, if possible, a letter) representing the region code. Thus, one might inaugurate the system either with eight regions, having region codes 202, 303, 404, 505, 606, 707, 808, and 909, and code a telephone number like (303)(412) 555-2121 as (432) 555-2121 in a computer database, or with eight areas within each region, having the numbers 212, 313, 414, 515, 616, 717, 818, and 919, thus coding (402)(313) 555-2121 as (432) 555-2121 in a computer database.

Copyright (c) 2001 John J. G. Savard


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