Telephone number

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A telephone number is a sequence of decimal digits that uniquely indicates the network termination point. The number contains the information necessary to identify the intended endpoint for the telephone call. Telephone numbers are often assigned to lines that have other devices connected such as faxes, modems, subscribers and network services. Each such endpoint must have a unique number within the public switched telephone network. Most countries use fixed length numbers (for normal lines at least) and therefore the number of endpoints determine the necessary length of the telephone number. It is also possible for each subscriber to have a set of shorter numbers for the endpoints most often used. These "shorthand" or "speed calling" numbers are automatically translated to unique telephone numbers before the call can be connected. Some special services have their own short numbers (e.g. 9-1-1, 4-1-1, 9-9-9 and 1-1-2). Many systems also allow calls within a local area to be made without dialing the local area code.

Most telephone networks nowadays are interconnected in the international telephone network, where the format of telephone numbers is standardized by ITU-T in the recommendation E.164, which specifies that the entire number should be 15 digits or shorter, and begin with a country prefix. For most countries, this is followed by an area code or city code and the subscriber number, which might consist of the code for a particular telephone switch. ITU-T recommendation E.123 describes how to represent an international telephone number in writing or print, starting with a plus sign ("+") and the country code. When calling an international number from a fixed line phone, the + must be replaced with the international call prefix chosen by the country the call is being made from. Mobile phones generally allow the + to be entered directly.

The format and allocation of local phone numbers are controlled by each nation's respective government, either directly or by sponsored organizations (such as NANPA overseen by NeuStar Inc.) See Telephone numbering plan.

Before a telephone call is connected, the telephone number must be dialed by the calling party or caller. The called party might have equipment that presents caller ID before the call is answered.

1 Business phones
2 History
3 Alphanumeric Trivia
4 Numeric Trivia
5 Intercepted number
6 See also
7 External links

[edit] Business phones

Businesses used to have a single telephone number for the main telephone switchboard of that business. A switchboard operator would connect the call within the business. If the called party didn't answer, the caller was typically transferred back to the switchboard. With voicemail and more technology, businesses now use Direct Inward Dialing (DID) (Direct Dialling Inwards (DDI) in the UK) lines so that outside callers can call to a specific person in a business. Often, the DID number uses a pattern from the called party's telephone internal extension. For example, within the Acme Corporation, a caller may dial 225 to reach Mr. Smith, but an outside caller may dial 448-9225 to reach Mr. Smith (with the last three digits representing Mr. Smith's extension). Some companies restrict the DDI capability to certain parts of the PABX or Centrex numbering range: Mr Smith on 225 might have it, but Mr Jones on 374 or Mr Brown on 427 would not. If a merger has happened in the past there may even be different exchange codes mapping to different parts of the internal numbering range. DID became an important feature of Centrex.

Some companies have a sufficient need for internal extensions that the whole numbering range following the exchange code (448 in the example) represents company extensions. A real example of this in the UK is the former Post Office's headquarters in Central London: the PABX was made an end node exchange in the London Director area, with the code 432. The automanual board was given the extension number 1234, so in the days before all-figure numbering outside callers reached the switchboard by dialing HEAdquarters 1234. The White House in Washington, DC is another example, having the (202)456 exchange.

[edit] History

In the late 1870s the Bell interests started exploiting their patent with a rental scheme, in which they would rent their instruments to individual users who would contract with other suppliers to connect them, for example from home to office to factory. Western Union and the Bell company both soon realized that a subscription service would be more profitable, with the invention of the telephone switchboard or central office. Such an office was staffed by an operator who connected the calls by personal names.

The latter part of 1879 and the early part of 1880 saw the first use of telephone numbers at Lowell, Massachusetts. During an epidemic of measles, Dr. Moses Greeley Parker feared that Lowell's four telephone operators might succumb and bring about a paralysis of telephone service. He recommended the use of numbers for calling Lowell's more than 200 subscribers so that substitute operators might be more easily trained in the event of such an emergency. Parker was convinced of the telephone's potential, began buying stock, and by 1883 he was one of the largest individual stockholders in both the American Telephone Company and the New England Telephone and Telegraph Company.

Even after the assignment of numbers, operators still connected most calls into the early 20th century; "Hello Central, get me Underwood-342." Connecting through operators or "Central" was usual until mechanical dialing of numbers became more common in the 1920s.

In rural areas with magneto crank telephones connected to party lines, the local phone number consisted of the line number plus the ringing pattern of the subscriber. To dial a number such as "3R122" meant making a request to the operator the third party line (if making a call off your own local one), followed by turning the telephone's crank once, a short pause, then twice and twice again. It was not uncommon to have over a dozen ringing patterns (and subscribers) on one line, and these systems were in use in a few remote areas of North America well into the 1970's. (See Bryant Pond, Maine.)

In North America, the digits 2-9 of phone numbers were allotted 3 letters of the alphabet apiece. In the UK, the letters O and Q were allocated to the digit 0, to reduce caller confusion among similar characters; digit 6 had only M and N, and digit 7 had P, R and S.

Phone numbers were not usually strictly numeric until the 1950s. From the 1920s until then, most urban areas had "exchanges" of two letters, followed by numbers. In the UK, however, exchanges in the major cities with Director installations were represented by three letters followed by four numbers; the letters usually represented the name of the exchange area (e.g. MAYfair, WATerloo), or something memorable about the locality (e.g. POPesgrove - an area where Alexander Pope once lived). This was considered easier to remember, although in London in the later part of this period it required the memorization of 7 characters (roughly the same number of characters as is usual for local calling in 2006). A word would represent the first two digits to be dialed, for example "TWinbrook" for "89" ; "BYwater" for "29". UK numbers had no letters at all except for those in the Director areas, where the first three of the seven digits were assigned letters, and written "ABBey 1234" or "WHItehall 1212", for example. A lack of pronounceable words, and the fact that most telephones world-wide have no letters on anyway, have led to the abandonment of letter usage in directory numbers except for publicity purposes.

The use of numbers starting in 555- (KLondike-5) to represent fake numbers in U.S. movies, television, and literature originated in this period, although valid numbers have since been assigned to the 555 exchange in most area codes.

Phone numbers were traditionally tied down to a single location, but the introduction of mobile telephones has changed this. In many countries, the practice of number portability allows customers to transfer a phone number from one local exchange carrier to another, or even from a fixed-line phone to a mobile phone.

[edit] Alphanumeric Trivia

Because the switches were hard-wired together and fairly hard to re-wire (or re-grade), telephone exchange buildings in many larger cities, in North America, were dedicated to circuits that began with the first two or three digits of the standard 7 digit phone numbers. In a holdover from the days of plug-board exchanges, the exchanges were typically named with a name whose first two letters translated to the digits of the exchange's prefix on a common telephone dial. Examples: CAstle (22), TRinity (87), MUtual (68). Certain number combinations were not amenable to this naming process, such as "57," "95" and "97;" it was in part due to this factor that telephone exchange names were eventually abandoned, as more numbers were needed to prevent a given area code from running out of available numbers.

In the past, the first two or three digits would map to a mnemonic exchange name, e.g. 869–1234 was formerly TOwnsend 9–1234, and before that (in some localities) might have been TOWnsend 1234 (only the capital letters and numbers being dialed).

In December of 1930, New York City became the first locality in the United States to adopt the two-letter, five-number format; it remained alone in this respect until well after World War II, when other municipalities across the country began to follow suit. From the 1920s through the 1950s, most larger U.S. cities used the Bell System standard format of two letters which began the exchange name followed by four numbers, as in DUnkirk 0799. Prior to the mid-1950s, the number immediately following the name could never be a "0" or "1;" indeed, "0" was never pressed into service at all, except in the immediate Los Angeles area (the "BEnsonhurst 0" exchange mentioned in an episode of the popular TV sitcom The Honeymooners was fictitious).

In 1955, the Bell System attempted to standardize the process of naming exchanges by issuing a "recommended list" of names to be used for the various number combinations. In 1961, New York Telephone introduced "selected-letter" exchanges, in which the two letters did not mark the start of any particular name (example: FL 6-9970), and by 1965 all newly-connected phone numbers nationwide consisted of numerals only (Wichita Falls, Texas had been the first locality in the United States to implement the latter, having done so in 1958). Pre-existing numbers continued to be displayed the old way in many places well into the 1970s. A Chicago carpet retailer frequently advertised their number NAtional 2-9000 on WGN until the 1990s; not to mention, the number TYler 8-7100 for a Detroit construction company, as well as another Chicago business, a carpet cleaning service, using HUdson 3-2700.

Most of the United Kingdom had no lettered telephone dials until the introduction of Subscriber Trunk Dialling (STD) in 1958. Prior to that time, only the director areas (Birmingham, Edinburgh, Glasgow, Liverpool, London and Manchester) and the non-director areas adjacent to them had lettered dials, and the director exchanges used the three-letter, four-number format. With the introduction of STD, the need for all callers to be able to dial numbers with letters in them led to the much more widespread use of lettered dials. The need for dials with letters was finally abandoned with the conversion to all-figure numbering in 1968.

Because the pulses in a Strowger switch exchange took time, having a phone number with lots of 8s or 9s or 0s meant it took longer to dial. The phone companies typically assigned such "high" numbers to pay phones because they were rarely dialed to.

To test the basic functioning of all of the switches in a chain, a special "test" number was reserved that consisted of all 5s (555–5555) — half-way up and in on each bank. The "555" (or KLondike) exchange was never assigned any real numbers (with limited exceptions such as 555-1212 for directory assistance), which is why today's TV and movie shows use 555-xxxx numbers for their phone numbers (previously, such productions often used numbers that ended in certain four-number combinations that were typically set aside for similar uses — "0079" on the West Coast and "9970" in many other places; examples include the TV series Perry Mason and the 1948 film Sorry, Wrong Number). That way there was no possibility that a fake number from a show would actually reach someone, thus avoiding the scenario which arose in 1982 with Tommy Tutone's hit single 867-5309/Jenny, which led to many customers who actually had that number receiving a plethora of unwanted calls. In fact, many US phone companies either no longer assign this number, or have relegated it to internal testing purposes.

However, today only numbers beginning with 555–01xx are reserved for fiction and other 555-numbers can be allocated to "information providers". A side effect of the fictional-number pool being reduced to 100 numbers is that the same ones now often recur in different movies or TV shows. The "958" and "959" exchanges have also been reserved for similar purposes in most localities, and as a result very few individuals or businesses have telephone numbers beginning with those sets of digits either (although this fact is not as well known, so such numbers have not been used in a fictional context).

The number in the Glenn Miller Orchestra's hit "PEnnsylvania 6-5000" was and is the number of the Hotel Pennsylvania in New York City. If you call the number, now written as (212) 736-5000, you still get the hotel.

[edit] Numeric Trivia

One of the most expensive phone numbers in the world is 666-6666 which was sold for USD$2.75 million in Doha, Qatar as part of a charity event in 2006.

Another is 888-8888, which was sold for USD$270,723 in Chengdu, China. 8 is traditionally considered a lucky number in Chinese culture.

Computer industry pioneer Steve Wozniak, a collector of phone numbers, obtained the phone number 888-8888, but it proved unusable: Children playing with phones would dial it, resulting in more than a hundred wrong numbers a day.[1]

[edit] Intercepted number

In the middle 20th century when a call could not be completed, for example because the phone number was not assigned, had been disconnected, or was in trouble, it went to an intercept operator who informed the caller. In the 1970s this service was converted to Automatic Intercept Systems which automatically chooses and presents an appropriate intercept message. Disconnected numbers may be reassigned after the rate of calls to them declines.