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87-477: A do not call list or do not call registry is a list of personal phone numbers that are off-limits to telemarketers in some countries. Do not call lists may also be held privately by a company, listing numbers that they will not call. This article related to telephony is a stub . You can help Misplaced Pages by expanding it . This marketing -related article is a stub . You can help Misplaced Pages by expanding it . Telephone number A telephone number

174-579: A 555 number . According to Universal Studios , which produced the movie, the number it used was picked because it did not exist in Buffalo, New York , where the movie was set. It did exist in other cities, resulting in customers' having that number receiving random calls from people asking for God. While some played along with the gag, others found the calls aggravating. The number in the Glenn Miller Orchestra 's hit song " Pennsylvania 6-5000 " (1940)

261-414: A private numbering plan for the installed base of telephones for internal communication. Such networks operate a private switching system or a private branch exchange (PBX) within the network. The internal numbers assigned are often called extension numbers , as the internal numbering plan extends an official, published main access number for the entire network. A caller from within the network only dials

348-451: 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. Some have argued that use of the telephone altered the physical layout of American cities. 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,

435-634: A switchboard operator when initiating a call. As telephone systems have grown and interconnected to encompass worldwide communication, telephone numbers have become longer. In addition to telephones , they have been used to access other devices, such as computer modems , pagers , and fax machines . With landlines , modems and pagers falling out of use in favor of all-digital always-connected broadband Internet and mobile phones , telephone numbers are now often used by data-only cellular devices, such as some tablet computers , digital televisions , video game controllers , and mobile hotspots , on which it

522-599: A telephone exchange . The exchange completes the call either to another locally connected subscriber or via the PSTN to the called party . Telephone numbers are assigned within the framework of a national or regional telephone numbering plan to subscribers by telephone service operators, which may be commercial entities, state-controlled administrations, or other telecommunication industry associations. Telephone numbers were first used in 1879 in Lowell, Massachusetts , when they replaced

609-423: A central access point to the PSTN and also controls internal calls between telephone extensions. In contrast to numbering plans, which determine telephone numbers assigned to subscriber stations, dialing plans establish the customer dialing procedures, i.e., the sequence of digits or symbols to be dialed to reach a destination. It is the manner in which the numbering plan is used. Even in closed numbering plans, it

696-412: A contacts application (akin to an electronic address book ) and the numbers no longer have to be written down or memorized. A telephone number serves as an address for switching telephone calls using a system of destination code routing. Telephone numbers are entered or dialed by a calling party on the originating telephone set, which transmits the sequence of digits in the process of signaling to

783-631: A director in Western Electric. His residence was phone number 1 and his shop was phone number 2 in Boston. In the late 1870s, the Bell interests started utilizing 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

870-486: A few nearby rate centres are considered long distance and incur toll fees. In a few large US cities, as well as many points outside North America, local calls are not flat-rated or "free" by default. Charles Williams, Jr., owned a Boston shop where Bell and Watson made experiments and later produced their telephones. This equipment company was purchased by Western Electric in 1882 and Williams became manager of this initial manufacturing plant until retiring in 1886, remaining

957-432: A mapping that was displayed directly on the telephone dial. Each of the digits 2 to 9, and sometimes 0, corresponded to a group of typically three letters. The leading two or three letters of a telephone number indicated the exchange name , for example, ED gewood and IV anhoe, and were followed by 5 or 4 digits. The limitations that these systems presented in terms of usable names that were easy to distinguish and spell, and

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1044-411: A maximum length of 15 digits to telephone numbers. The standard defines a country code for each member region which is prefixed to each national telephone number for international destination routing . Private numbering plans exist in telephone networks that are privately operated in an enterprise or organizational campus. Such systems may be supported by a private branch exchange (PBX), which provides

1131-410: A numbering plan became known as a closed numbering plan . In several European countries, a different strategy prevailed, known as the open numbering plan , which features a variance in the length of the area code, the local number, or both. The subscriber number is the address assigned to a telephone line or wireless communication channel terminating at the customer equipment. The first few digits of

1218-453: A prefix (such as '8') followed by an internal routing code to indicate a city or location, then an individual four- or five-digit extension number at the destination site. A common trunk prefix for an outside line on North American systems is the digit 9, followed by the outside destination number. Additional dial plan customisations, such as single-digit access to a hotel front desk or room service from an individual room, are available at

1305-532: A real subscriber. The 555 code is used in the Balmain area of Sydney and the suburbs of Melbourne . Although in many areas being a prefix of 55 plus the thousand digit of 5 (e.g. 55 5XXX), would be valid, the numbering system was changed so that 555 became 9555 in Sydney and Melbourne, and in the country, there are two new digits ahead of the 55. Tommy Tutone 's 1981 hit song " 867-5309/Jenny " led to many unwanted calls by

1392-683: A subscriber to request moving an existing telephone number to another telephone service provider. Number portability usually has geographic limitations, such as an existing local telephone company only being able to port to a competitor within the same rate centre . Mobile carriers may have much larger market areas, and can assign or accept numbers from any area within the region. In many telephone administrations, mobile telephone numbers are in organized in prefix ranges distinct from land line service, which simplifies mobile number portability , even between carriers. Within most North American rate centres, local wireline calls are free, while calls to all but

1479-760: A telephone number consist of a country code and a national telephone number. National telephone numbers are defined by national or regional numbering plans, such as the European Telephony Numbering Space , the North American Numbering Plan (NANP), or the UK number plan . Within a national numbering plan, a complete destination telephone number is typically composed of an area code and a subscriber telephone number. Many national numbering plans have developed from local historical requirements and progress or technological advancements, which resulted in

1566-472: A variance in the length of the area code, local number, or both of a telephone number assigned to a subscriber line. The latter type developed predominantly in Europe. The International Telecommunication Union (ITU) has established a comprehensive numbering plan, designated E.164 , for uniform interoperability of the networks of its member state or regional administrations. It is an open numbering plan but imposes

1653-456: A variety of structural characteristics of the telephone numbers assigned to telephones. In the United States, the industry decided in 1947 to unite all local telephone networks under one common numbering plan with a fixed length of ten digits for the national telephone number of each telephone, of which the last seven digits were known as the local directory number , or subscriber number . Such

1740-459: A varying count of digits. Irrespective of the type of numbering plan, "shorthand" or "speed calling" numbers are automatically translated to unique telephone numbers before the call can be connected. Some special services have special short codes (e.g., 119 , 911 , 100 , 101, 102, 000 , 999 , 111 , and 112 being the emergency telephone numbers in many countries). The dialing procedures ( dialing plan ) in some areas permit dialing numbers in

1827-452: Is a sequence of digits assigned to a landline telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices for data transmission via the public switched telephone network (PSTN), or other public and private networks. Modern smart phones have added a built-in layer of abstraction whereby individuals or businesses are saved into

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1914-558: Is a set of digits forming the most-significant part of the dialing sequence to reach a telephone subscriber. Numbering plans may follow a variety of design strategies which have often arisen from the historical evolution of individual telephone networks and local requirements. A broad division is commonly recognized between closed and open numbering plans. A closed numbering plan , as found in North America, features fixed-length area codes and local numbers, while an open numbering plan has

2001-451: Is an international numbering plan and establishes a country calling code ( country code ) for each member organization. Country codes are prefixes to national telephone numbers that denote call routing to the network of a subordinate number plan administration, typically a country, or group of countries with a uniform numbering plan, such as the NANP. E.164 permits a maximum length of 15 digits for

2088-483: Is not always necessary to dial all digits of a number. For example, an area code may often be omitted when the destination is in the same area as the calling station. National or regional telecommunication administrations that are members of the International Telecommunication Union (ITU) use national telephone numbering plans that conform to international standard E.164 . E.164 specifies that

2175-418: Is not even possible to make or accept a call . The number contains the information necessary to identify the intended endpoint for a telephone call . Many countries use fixed-length numbers in a so-called closed numbering plan . A prominent system of this type is the North American Numbering Plan . In Europe, the development of open numbering plans was more prevalent, in which a telephone number comprised

2262-421: Is often called a dial plan . A dial plan establishes the expected sequence of digits dialed on subscriber premises equipment, such as telephones, in private branch exchange (PBX) systems, or in other telephone switches to effect access to the telephone networks for the routing of telephone calls, or to effect or activate specific service features by the local telephone company, such as 311 or 411 service. Within

2349-405: Is particularly useful in multilingual contexts as the tone indicates an error has been encountered, even if the message cannot be understood by the caller and can be interpreted as an error by some auto-dialling equipment. Telephone numbers are sometimes prefixed with special services, such as vertical service codes , that contain signaling events other than numbers, most notably the star (*) and

2436-561: Is the number of the Hotel Pennsylvania in New York City . The number is now written as 1-212-736-5000. According to the hotel's website, PEnnsylvania 6-5000 is New York's oldest continually assigned telephone number and possibly the oldest continuously-assigned number in the world. Australian films and television shows do not employ any recurring format for fictional telephone numbers; any number quoted in such media may be used by

2523-669: The MSISDN is longer than 20 digits then additional digits are encoded into extension blocks (EF EXT1 ) each having a BCD-encoded field of 11 bytes. This scheme allows to extend the subscriber number with a maximum of 20 digits by additional function values to control network services . In the context of ISDN the function values were transparently transported in a BCD-encoded field with a maximum of 20 bytes named "ISDN Subaddress". The format and allocation of local telephone numbers are controlled by each nation's respective government, either directly or by sponsored organizations (such as NANPA in

2610-429: The UK , letters were assigned to numbers in a similar fashion to North America, except that the letter O was allocated to the digit 0 (zero); digit 6 had only M and N. The letter Q was later added to the zero position on British dials, in anticipation of direct international dialing to Paris, which commenced in 1963. This was necessary because French dials already had Q on the zero position, and there were exchange names in

2697-601: The number sign (#). Vertical service codes enable or disable special telephony services either on a per-call basis, or for the station or telephone line until changed. The use of the number sign is most frequently used as a marker signal to indicate the end of digit sequences or the end of other procedures; as a terminator it avoids operational delays when waiting for expiration of automatic time-out periods. Fictitious telephone numbers are often used in films and on television to avoid disturbances by calls from viewers. For example, The United States 555 (KLondike-5) exchange code

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2784-423: 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. Also common

2871-574: The ITU standard Q.713 , paragraph 3.4.2.3.3, indicating the numbering plan of the attached telephone number. NPIs can be found in Signalling Connection Control Part (SCCP) and short message service (SMS) messages. As of 2004 , the following numbering plans and their respective numbering plan indicator values have been defined: While a telephone numbering plan specifies the digit sequence assigned to each telephone or wire line, establishing

2958-440: The NANP had at times specific restrictions on the range of digits for the three positions, and required assignment to geographical areas avoiding nearby areas receiving similar area codes to avoid confusion and misdialing. Some countries, such as Denmark and Uruguay , have merged variable-length area codes and telephone numbers into fixed-length numbers that must always be dialed independently of location. In such administrations,

3045-589: The NANP have three digits, while two digits are used in Brazil , one digit in Australia and New Zealand . Variable-length formats exist in multiple countries including: Argentina , Austria (1 to 4), Germany (2 to 5 digits), Japan (1 to 5), Mexico (2 or 3 digits), Peru (1 or 2), Syria (1 or 2) and the United Kingdom . In addition to digit count, the format may be restricted to certain digit patterns. For example,

3132-492: The North American Numbering Plan (NANP), the administration defines standard and permissive dialing procedures, specifying the number of mandatory digits to be dialed for local calls within a single numbering plan area (NPA), as well as alternate, optional sequences, such as adding the prefix 1 before the telephone number. Despite the closed numbering plan in the NANP, different dialing procedures exist in many of

3219-463: The Paris region which contained the letter Q. Most of the United Kingdom had no lettered telephone dials until the introduction of Subscriber Trunk Dialing (STD) in 1958. Until then, only the director areas (Birmingham, Edinburgh, Glasgow, Liverpool, London and Manchester) and the adjacent non-director areas had the lettered dials; the director exchanges used the three-letter, four-number format. With

3306-662: The US or CNAC in Canada). In the United States, each state's public service commission regulates, as does the Federal Communications Commission . In Canada, which shares the same country code with the U.S. (due to Bell Canada 's previous ownership by the U.S.-based Bell System ), regulation is mainly through the Canadian Radio-television and Telecommunications Commission . Local number portability (LNP) allows

3393-478: The United States and Canada into numbering plan areas (NPAs), and assigned to each NPA a unique three-digit prefix, the numbering plan area code , which became known in short-form as NPA code or simply area code . The area code is prefixed to each telephone number issued in its service area. Other national telecommunication authorities use various formats and dialing rules for area codes. The size of area code prefixes may either be fixed or variable. Area codes in

3480-439: The area code in parentheses, signifying that in some cases the area code is optional or may not be required. Internationally, an area code is typically prefixed by a domestic trunk access code (usually 0) when dialing from inside a country, but is not necessary when calling from other countries; there are exceptions, such as for Italian land lines . To call a number in Sydney, Australia , for example: The plus character (+) in

3567-499: The area code into the subscriber's number. This usually makes the use of a trunk code obsolete. For example, to call someone in Oslo in Norway before 1992, it was necessary to dial: After 1992, this changed to a closed eight-digit numbering plan, e.g.: However, in other countries, such as France , Belgium , Japan , Switzerland , South Africa and some parts of North America, the trunk code

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3654-458: The area code is not distinguished formally in the telephone number. In the UK, area codes were first known as subscriber trunk dialling (STD) codes. Depending on local dialing plans, they are often necessary only when dialed from outside the code area or from mobile phones. In North America ten-digit dialing is required in areas with overlay numbering plans , in which multiple area codes are assigned to

3741-463: The area code to be dialed when calling between two local calling areas. During the 1970s and 1980s, each local calling area had its own area code. For example, Christchurch and Nelson in the late 1980s: During the early 1990s, the numbering plan was reorganised with the numerous area codes merged into just five, but the requirement to dial the area code between local calling areas remained. This means even though Christchurch and Nelson are now both in

3828-421: The area code within the same area code, even if no area code is required, has been permitted since the mid-2000s. For example, in the 559 area code (a non-overlay area code), calls may be dialed as seven digits (XXX-XXXX) or 1 559 + 7 digits. The manner in which a call is dialed does not affect the billing of the call. This "permissive home area code dialing" helps maintain uniformity and eliminates confusion given

3915-549: The area code, or 1 and the area code, is required even for local calls. Dialing from mobile phones does not require the trunk code in the US, although it is still necessary for calling all long-distance numbers from a mobile phone in Canada. Many mobile handsets automatically add the area code of the set's telephone number for outbound calls, if not dialed by the user. In some parts of the United States, especially northeastern states such as Pennsylvania served by Verizon Communications ,

4002-497: The area. Special telephone numbers are used for high-capacity numbers with several telephone circuits , typically a request line to a radio station where dozens or even hundreds of callers may be trying to call in at once, such as for a contest. For each large metro area , all of these lines will share the same prefix (such as 404 -741- xxxx in Atlanta and 305 -550- xxxx in Miami ),

4089-468: The call is being made from. Many mobile phones allow the + to be entered directly, by pressing and holding the "0" for GSM phones, or sometimes "*" for CDMA phones. The 3GPP standards for mobile networks provide a BCD-encoded field of ten bytes for the telephone number ("Dialling Number/SCC String"). The international call prefix or "+" is not counted as it encodes a value in a separate byte (TON/NPI - type of number / numbering plan identification). If

4176-492: The complete international phone number consisting of the country code, the national routing code (area code), and the subscriber number. E.164 does not define regional numbering plans, however, it does provide recommendations for new implementations and uniform representation of all telephone numbers. Country codes are necessary only when dialing telephone numbers in other countries than the originating telephone, but many networks permit them for all calls. These are dialed before

4263-550: The dialed digits while cellphone users can omit the "1" and just dial 10 digits. Many organizations have private branch exchange systems which permit dialing the access digit(s) for an outside line (usually 9 or 8), a "1" and finally the local area code and xxx xxxx in areas without overlays. This aspect is unintentionally helpful for employees who reside in one area code and work in an area code with one, two, or three adjacent area codes. 1+ dialing to any area code by an employee can be done quickly, with all exceptions processed by

4350-569: The different types of area code relief that has made California the nation's most "area code" intensive State. Unlike other states with overlay area codes (Texas, Maryland, Florida and Pennsylvania and others), the California Public Utilities Commission and the New York State Public Service Commission maintain two different dial plans: Landlines must dial 1 + area code whenever an Area Code is part of

4437-546: The exchange. The North American Numbering Plan of 1947 prescribed a format of telephone numbers that included two leading letters of the name of the central office to which each telephone was connected. This continued the practice already in place by many telephone companies for decades. Traditionally, these names were often the names of towns, villages, or were other locally significant names. Communities that required more than one central office may have used other names for each central office, such as "Main", "East", " Central" or

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4524-406: The extension number assigned to another internal destination telephone. A private numbering plan provides the convenience of mapping station telephone numbers to other commonly used numbering schemes in an enterprise. For example, station numbers may be assigned as the room number of a hotel or hospital. Station numbers may also be strategically mapped to certain keywords composed from the letters on

4611-463: The full number with area and access codes. The subscriber number is typically listed in local telephone directories, and is therefore often referred to as the directory number . Telephone administrations that manage telecommunication infrastructure of extended size, such as a large country, often divide the territory into geographic areas. This benefits independent management by administrative or historical subdivisions, such as states and provinces, of

4698-416: The introduction of trunk dialing, 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 ceased with the conversion to all-digit numbering in 1968. In the middle 20th century in North America when a call could not be completed, for example because the phone number was not assigned, had been disconnected, or

4785-457: The last digits typically corresponding to the station's frequency , callsign , or moniker . In the international telephone network, the format of telephone numbers is standardized by ITU-T recommendation E.164 . This code specifies that the entire number should be 15 digits or shorter, and begin with an international calling prefix and a country prefix . For most countries, this is followed by an area code, city code or service number code and

4872-402: The local area. An attempt to dial a 555 number from a movie in the United States results in an error message. This reduces the likelihood of nuisance calls. QU incy(5–5555) was also used, because there was no Q available. Phone numbers were traditionally tied down to a single location; because exchanges were "hard-wired", the first three digits of any number were tied to the geographic location of

4959-429: The local calling area without using an area code or city code prefix. For example, a telephone number in North America consists of a three-digit area code, a three-digit central office code, and four digits for the line number. If the numbering plan area does not use an overlay plan with multiple area codes, or if the provider allows it for other technical reasons, seven-digit dialing may be permissible for calls within

5046-406: The markup signifies that the following digits are the country code, in this case 61. Some phones, especially mobile telephones, allow the + to be entered directly. For other devices the user must replace the + with the international access code for their current location. In the United States, most carriers require the caller to dial 011 before the destination country code. New Zealand requires

5133-468: The names of local districts. Names were convenient to use and reduced errors when telephone numbers were exchanged verbally between subscribers and operators. When subscribers could dial themselves, the initial letters of the names were converted to digits as displayed on the rotary dial. Thus, telephone numbers contained one, two, or even three letters followed by up to five numerals. Such numbering plans are called 2L-4N, or simply 2–4, for example, as shown in

5220-497: The national access code. For example, a number in London may be listed as 020 7946 0321 . Users must correctly interpret 020 as the code for London. If they call from another station within London, they may merely dial 7946 0321 , or if dialing from another country, the initial 0 should be omitted after the country code. The E.164 standard of the International Telecommunication Union

5307-502: The national telephone number. Following ITU-T specification E.123 , international telephone numbers are commonly indicated in listings by prefixing the country code with a plus sign ( + ). This reminds the subscriber to dial the international access code of the country from which the call is placed. For example, the international dialing prefix or access code in all NANP countries is 011 , and 00 in most other countries. On modern mobile telephones and many voice over IP services,

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5394-448: The need for a comprehensive numbering plan that enabled direct-distance dialing, led to the introduction of all-number dialing in the 1960s. The use of numbers starting in 555- ( KL ondike-5) to represent fictional numbers in U.S. movies, television, and literature originated in this period. The "555" prefix was reserved for telephone company use and was only consistently used for directory assistance (information), being "555–1212" for

5481-409: The network addresses needed for routing calls, numbering plan administrators may define certain dialing procedures for placing calls. This may include the dialing of additional prefixes necessary for administrative or technical reasons, or it may permit short code sequences for convenience or speed of service, such as in cases of emergency. The body of dialing procedures of a numbering plan administration

5568-707: The official telephone number with the extension number, e.g., 1 800 555-0001 x2055. Some systems may automatically map a large block of DID numbers (differing only in a trailing sequence of digits) to a corresponding block of individual internal stations, allowing each of them to be reached directly from the public switched telephone network . In some of these cases, a special shorter dial-in number can be used to reach an operator who can be asked for general information, e.g. help looking up or connecting to internal numbers. For example, individual extensions at Universität des Saarlandes can be dialed directly from outside via their four-digit internal extension +49-681-302-xxxx, whereas

5655-535: The photo of a telephone dial of 1939 (right). In this example, LA kewood 2697 indicates that a subscriber dialed the letters L and A , then the digits 2 , 6 , 9 , and 7 to reach this telephone in Lakewood, NJ (USA). The leading letters were typically bolded in print. In December 1930, New York City became the first city in the United States to adopt the two-letter and five-number format (2L-5N), which became

5742-412: The physician, Dr. Moses Greeley Parker, feared that Lowell's four telephone operators might all succumb to sickness and bring about 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 such an emergency. Parker was convinced of the telephone's potential, began buying stock, and by 1883 he

5829-429: The plus sign can usually be dialed and functions directly as the international access code. Peer-to-peer SIP uses Dynamic Delegation Discovery System to perform endpoint discovery, and therefore E.164 numbers. Within the system of country calling codes, the ITU has defined certain prefixes for special services, and assigns such codes for independent international networks, such as satellite systems, spanning beyond

5916-415: The private branch exchange and passed onto the public switched telephone network . In small countries or areas, the full telephone number is used for all calls, even in the same area. This has traditionally been the case in small countries and territories where area codes have not been required. However, there has been a trend in many countries towards making all numbers a standard length, and incorporating

6003-418: The public to telephone subscribers who actually were assigned that number. Closed numbering plan For public numbering systems, geographic location typically plays a role in the sequence of numbers assigned to each telephone subscriber. Many numbering plan administrators subdivide their territory of service into geographic regions designated by a prefix, often called an area code or city code , which

6090-604: The request for subscriber names by callers connecting to the switchboard operator . Over the course of telephone history , telephone numbers had various lengths and formats and even included most letters of the alphabet in leading positions when telephone exchange names were in common use until the 1960s. Telephone numbers are often dialed in conjunction with other signaling code sequences, such as vertical service codes , to invoke special telephone service features. When telephone numbers were first used they were very short, from one to three digits, and were communicated orally to

6177-474: The same area code, the area code has to be dialed for calls between the two cities. In many areas of the NANP, the domestic trunk code (long-distance access code) must also be dialed along with the area code for long-distance calls even within the same numbering plan area. For example, to call a number in Regina in area code 306 : In many parts of North America, especially in area code overlay complexes , dialing

6264-487: The same area. The strict correlation of a telephone number to a geographical area has been broken by technical advances, such as local number portability in the North American Numbering Plan and voice over IP services. When dialing a telephone number, the area code may have to be preceded by a trunk prefix or national access code for domestic calls, and for international calls by the international access code and country code. Area codes are often quoted by including

6351-486: The scope of regional authorities. Some special service codes are the following: Satellite phones are typically issued with telephone numbers with a special country calling code, for example: Some satellite telephones are issued with telephone numbers from a national numbering plan; for example, Globalstar issues NANP telephone numbers. Like a public telecommunications network, a private telephone network in an enterprise or within an organizational campus may implement

6438-464: The sole discretion of the PBX owner. Signaling in telecommunication networks is specific to the technology in use for each link. During signaling, it is common that additional information is passed between switching systems that is not represented in telephone numbers, which serve only as network addresses of endpoints. One such information element is the numbering plan indicator (NPI). It is a number defined in

6525-455: The standard after World War II , when the Bell System administration designed the North American Numbering Plan to prepare the United States and Canada for Direct Distance Dialing (DDD), and began to convert all central offices to this format. This process was complete by the early 1960s, when a new numbering plan, often called all number calling (ANC) became the standard in North America. In

6612-435: The subscriber number may indicate smaller geographical scopes, such as towns or districts, based on municipal aspects, or individual telephone exchanges ( central office code ), such as a wire centers. In mobile networks they may indicate the network provider. Callers in a given area sometimes do not need to include area prefixes when dialing within the same area, but devices that dial telephone numbers automatically may include

6699-404: The subscriber number, which might consist of the code for a particular telephone exchange . 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 landline phone, the + must be replaced with the international call prefix chosen by the country

6786-476: The telephone dial, such as 4357 ( help ) to reach a help desk . The internal number assignments may be independent of any direct inward dialing (DID) services provided by external telecommunication vendors. For numbers without DID access, the internal switch relays externally originated calls via an operator, an automated attendant or an electronic interactive voice response system. Telephone numbers for users within such systems are often published by suffixing

6873-422: The ten-digit number must be dialed. If the call is not local, the call fails unless the dialed number is preceded by digit 1. Thus: In California and New York, because of the existence of both overlay area codes (where an area code must be dialed for every call) and non-overlay area codes (where an area code is dialed only for calls outside the subscriber's home area code), "permissive home area code dialing" of 1 +

6960-446: The territories for local and long-distance telephone calls. This means that to call another number within the same city or area, callers need to dial only a subset of the full telephone number. For example, in the NANP, only the seven-digit number may need to be dialed, but for calls outside the local numbering plan area, the full number including the area code is required. In these situations, ITU-T Recommendation E.123 suggests to list

7047-407: The territory or country. Each area of subdivision is identified in the numbering plan with a routing code. This concept was first developed in the planning for a nationwide numbering plan for Operator Toll Dialing and direct distance dialing (DDD) in the Bell System in the United States in the 1940s, a system that resulted in the North American Numbering Plan for World Zone 1. AT&T divided

7134-472: The university's official main number is +49-681-302-0 (49 is the country code for Germany , 681 is the area code for Saarbrücken , 302 the prefix for the university). Callers within a private numbering plan often dial a trunk prefix to reach a national or international destination ( outside line ) or to access a leased line (or tie-line ) to another location within the same enterprise. A large manufacturer with factories and offices in multiple cities may use

7221-437: Was a code of long and short rings, so one party's call might be signaled by two longs and another's by two longs followed by a short. It was not uncommon to have over a dozen ring cadences (and subscribers) on one line. In most areas of North America , telephone numbers in metropolitan communities consisted of a combination of digits and letters, starting in the 1920s until the 1960s. Letters were translated to dialed digits,

7308-441: Was experiencing technical difficulties, the call was routed to an intercept operator who informed the caller. In the 1970s this service was converted to Automatic Intercept Systems which automatically choose and present an appropriate intercept message . Disconnected numbers are reassigned to new users after the rate of calls to them declines. Outside of North America operator intercept was rare, although it did exist, for example it

7395-489: Was never assigned (with limited exceptions such as 555–1212 for directory assistance ). Therefore, American films and TV shows have used 555-xxxx numbers, in order to prevent a number used in such a work from being called. The film Bruce Almighty (2003) originally featured a number that did not have the 555 prefix. In the cinematic release, God ( Morgan Freeman ) leaves 776–2323 on a pager for Bruce Nolan ( Jim Carrey ) to call if he needed God's help. The DVD changes this to

7482-538: 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 the norm until mechanical direct-dialing of numbers became more common in

7569-482: Was sometimes used in Ireland . However, in most cases, calls to unassigned or disconnected numbers resulted in an automated message, either giving specific or a generic recorded error message. Some networks and equipment simply returned a number unobtainable , reorder or SIT (special information) tone to indicate an error. In some networks recordings for error messages were (and still are) preceded by an SIT tone. This

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