The number crunch monster: Adding more digits is not likely to solve the number shortage, but a new addressing system might stare down the dilemma

The number crunch monster: Adding more digits is not likely to solve the number shortage, but a new addressing system might stare down the dilemma

Moishe Garfinkle

The number of available telephone addresses is dwindling rapidly even as the number of requests for new addresses accelerates.

Although the number of lines requested for POTS is increasing at a moderate rate that has not changed significantly in the past decade, the number of lines sought for ancillary devices such as fax machines, cellular phones, modems and pagers has skyrocketed (Figure 1).

What happened, and what now?

Instead of relying on a variation of the familiar North American Numbering Plan, an alternative called the multifunctional telecommunication addressing system might be the answer to the numbering dilemma.

A number black hole To understand why, it’s necessary to recall how the numbering system works. The NANP addressing arrangement comprises 10 digits-n (abc) def-hijk-in which hijk is the subscriber’s line number, def is the central office exchange number, and abc is the area code for a specific geographic region denoted in the numbering plan area.

This fixed grouping also serves mnemonic purposes: By separating the telephone address into specific groups of characters, subscribers can more readily remember their addresses. For calls within a plan, only the CO exchange and line number are required to reach the intended party-seven digits in all. For calls between any plan areas, all 10 digits are required.

So that the public network can distinguish between a seven-digit local call and a 10-digit long-distance call, an access code “n” is placed before the 10-digit address, either a zero or a one. Fortunately, the first digit of the CO exchange is restricted to numbers between two and nine because old rotary dials did not have letters for the one dialing position, and position zero signaled the operator. So local calls cannot begin with a zero or a one-only long-distance calls (Figure 2).

This addressing arrangement was designed to accommodate today’s explosive increase in requested addresses, and it should have, except for a rather serious miscalculation in allotting the addresses.

As originally conceived, each plan area would have a single area code. However, as the need for new addresses exceeded the addresses available in each area, two remedies were applied.

Either the area affected was split, introducing a new area code, or two area codes were assigned, the latter requiring that all calls within that area use 10 digits, whether local or long-distance. Public resistance has pretty well killed this overlay approach.

Remarkably, however, the NANP provides 6.4 billion possible addresses for public service. Discounting addresses for testing, maintenance and special services, only 5% of these 6.4 billion possible addresses are actually in service.

The primary reason for this poor usage is that every CO exchange can accommodate 10,000 line numbers from 0000 to 9999 but because the CO exchange is a physical building that houses the public network switches, the CO exchange can be fully used only if 10,000 subscribers are in its region.

If an exchange region has only 200 subscribers, 98% of the available telephone addresses are unused and effectively lost. In contrast, if an exchange region is saturated and subsequently divided using a new exchange facility, then for an extended period both CO exchanges accommodate roughly 50% of their innate capacity. In other words, the NANP can accommodate almost 20 times the number of addresses in actual service, except that most of these are unused or unusable.

However, to totally revamp NANP at this late date is both politically inconceivable and technically impractical. Any proposed remedy must adhere to the NANP protocol.

In response to this perceived loss in available telephone addresses, the Industry Numbering Committee of the Alliance for Telecommunications Industry Solutions has discarded as impractical any further attempts to significantly increase the number of available telephone addresses while adhering to the existing 10-digit addressing protocol.

Every option has its drawbacks To head off an addressing calamity, the INC is considering several expansion options grouped under the long-term numbering plan. Although the public network can handle addresses up to 16 digits under the NANP protocol, the number of address digits in this plan will not exceed 12 characters to remain within accepted international connectivity recommendations.

About a dozen options exist under the long-term plan, but these can be classified in four general categories, all of which require increasing the number of digits in telephone addresses in the NANP service area. Essentially, a new bound-group arrangement is to be used requiring a new mnemonic, but this arrangement would be fixed for all NANP addresses, and so would the new mnemonic.

The options can be categorized as follows: * Increase line number digits from four to five-n (abc) def-ghijk. This is the most straightforward and least disruptive approach, but the least compatible with the present addressing arrangement.

* Increase CO exchange digits from three to four-n (abc) defg-hijk. The d character would still be restricted to digits between two and nine for NANP compatibility. But because COs are physical structures, this approach would probably be the most difficult to implement.

* Increase area code digits from three to four-n (abcd) efg-hijk. Although the a character would still be restricted to digits between two and nine, the number of numbering plan areas would increase significantly, fragmenting already sub-divided areas. The result would be a multitude of plan areas so small that most calls would be long-distance, essentially resulting in full 12-character addressing.

* Introduce a national destination code to distinguish between countries served by the NANP-nxx (abc) def-hijk. Callers would use the code when calling from one country to another in the NANP service area. Several variations exist for national destination code, depending on the number of digits in the code and the position of the code in the address.

The long-term numbering plan categories involve lengthening telephone addresses rather than increasing the functionality of the addresses already in service. Essentially, the plan will increase the number of possible addresses tenfold to about 60 billion. The long-term options constitute no more than a brute-force approach.

In addition, implementing the long-term numbering plan will be quite troublesome because it is not particularly compatible with public network addressing. A transition period will be difficult to arrange because the public network switches will not be able to recognize a priority whether the address dialed had one more or one less digit. In fact, the question of compatibility is one of the principal difficulties in choosing any of the current long-term plan options.

Public resentment over changing everybody’s telephone address in the NANP service area would be matched by public resentment over additional digits to be remembered and dialed.

That the present long-term numbering plan options cannot be readily implemented may be their only saving grace.

An answer may lie in the symbols Consider now the multifunctional telecommunication addressing system.

Although the system changes the number of characters required to access various telecom devices, the additional characters are not numerical and therefore do not enter directly into subscribers’ primary telephone addresses.

The symbol keys designated * and # are not used in telephone addressing, although they are used by automated devices and special subscriber services. Simply adding these keys to new telephone addresses would lead to the same confusion as adding additional characters and would add significant mnemonic difficulties, leading to increased misdialing.

These two symbols serve as markers or place-setters designating the type of telecom equipment to be accessed, according to the system protocol.

Local telephone addresses are represented in the familiar public network fixed group arrangement of two bound groups separated by a divider-def-hijk.

Although most people do not consciously remember the group divider, it remains part of the array stored in their memories. When they recall a telephone address, they recall the divider by pausing when reciting or recording the address.

Essentially, people do not recall the local address as a single bound group but as an array of two bound groups. The local address shown is designated as the subscriber’s primary address, according to the protocol. Based on this primary address, a series of sub-addresses is created by placing markers between the bound groups for multifunctional purposes-either * or #.

Not only is the expected address preserved as two bound groups with a divider, but the marker also fits comfortably between the bound groups. The mnemonic is preserved. Because the marker is not a numerical character, it cannot be confused with the address.

Consider the multifunctional telecom addressing system in practice. A business subscriber has two lines, for example-a regular telephone line and a fax line. The telephone address is 321-1234 and the fax address is 321-2345 (Figure 2).

The subscriber could change his fax address to a sub-address using the marker doublet ** so that the addresses are 321-1234 for telephone and 321**1234 for fax, with each still an independent, autonomous and distinct line. In both cases, the telephone address terminates with a four-digit line number, signaling the end of the address sequence as expected by the public network.

There are now extra characters, but the user doesn’t perceive it because it does not require another address character nor a change in the conventional bound character grouping.

The ** doublet serves solely as a marker and indicates to the public network that a fax machine is being accessed. Because the switch recognizes the * tone, it is a matter of programming the network software to secure the correct interconnection.

Most important, the multifunctional addressing system is invisible after it has been implemented until a subscriber requests a system. Hence, the system is absolutely compatible with the present addressing arrangement.

As in conventional practice, the subscriber’s fax machine would be accessible by both the old and new addresses for a transition period after the multifunctional system is introduced. Area codes would have no effect on this arrangement.

Most significantly, however, the fax address released for reuse, 321-2345, could accommodate two lines of another subscriber.

The functionality of the system can be further expanded by using the # symbol. A salesperson often needs a cellular phone on the road, and it would be both convenient and smart from a sales viewpoint if its sub-address was the same as his or her primary telephone address, for example, 321-1234 for telephone, 321**1234 for fax and 321##1234 for cellular.

Therefore, the impact of fax machines and cellular phones on the number of available telephone addresses can be improved significantly.

If the salesperson has a laptop computer, a virtual necessity these days, the modem sub-address would be 321*#1234 and a pager’s sub-address would be 321#*1234 (Figure 3).

Although additional characters are present, the public network switch recognizes them. The correct interconnection is a matter of programming the public network. Essentially, the salesperson’s five lines function independently because each has a distinct address. The sub-addresses are simply expected variations on the primary address.

The multifunctional system also can accommodate devices not yet commercially available or even devised by using marker triplets as well as doublets (Figure 4). There are eight triple-marker combinations. When videophones proliferate, the system can accommodate them. All sub-address lines operate autonomously and when needed, simultaneously.

As telephone addresses are recycled, a new series of sub-addresses is created. Because the number of lines requested for ancillary devices such as fax machines and cellular phones is increasing far more rapidly than line requests for telephone service, the addresses released for recycling will exceed the number of lines requested for new telephone service, at least for the foreseeable future.

The selection of the specific markers to be assigned to each of these telecommunications devices would probably be the responsibility of the NANP administrator, along with the INC and the FCC’s North American Numbering Council.

Additional telephone addresses are required for special services such as asynchronous transfer mode lines, check and credit card verification, and security systems. Moreover, utilities are planning to implement automatic residential meter reading by computer, requiring a multitude of additional telephone addresses (Figure 5).

Inasmuch as these special services are automatically dialed local connections, their requirements can be readily met by the multifunctional addressing system using multiple symbols, further increasing the functionality of available telephone addresses, allowing the familiar public network address arrangement to be preserved throughout the NANP service area. The system is discussed in further detail at

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