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1000-banks or

See “Telephone Number Components.”


100-banks or


See “Telephone Number Components.”


Area Code


See “Telephone Number Components.”




An electronic device that can automatically dial telephone numbers to communicate between any two points in the telephone network. Once the call has been established the autodialer can provide verbal messages or transmit digital data (like SMS messages) to the called party. A predictive dialer is a computerized system that automatically dials batches of telephone numbers for connection to interviewers or telemarketing agents. They can also reject numbers that do not make a connection. Predictive dialers are widely used in call centers. The FCC has placed a variety of restrictions on the use of such devices, including a general prohibition that such computerized equipment cannot be used by anyone to initiate calls to wireless devices (cell phones, pagers, etc).




See “Telcordia/Bellcore.”


Cell Phone


A generic term for a portable wireless electronic device used for wireless communication. Current cell phones can support many additional services such as SMS for text messaging, e-mail, packet switching for access to the Internet, and MMS for sending and receiving photos and video. Outside the United States these devices are commonly referred to as mobile phones.




A form of wireless communication where wireless telephone calls connect to a cellular network of base stations (cell sites), which is in turn interconnect to the public switched telephone network. Cellular phones operate in the 824-894 MHz frequency range. Originally, cellular licensees were required provide analog service in addition to digital service, but this requirement ended on February 18, 2008.
As cellular licensees have converted from analog service to digital service they have generally adopted the GSM standard for mobile phones allowing them to compete with PCS licensees. See “Cell Phone,” “Personal Communications Service (PCS),” “Wireless” and GSM.


Dual Frame Sampling


Occurs when a sample is selected from two potentially overlapping frames. For example, a sample of listed telephone numbers supplemented with a RDD sample. The overlap, units that appear in both frames, must be identified and accounted for.




See “Telephone Number Components.”




GSM stands for Global System for Mobile communications or Groupe Special Mobile. GSM uses a cellular network and is the most popular standard for mobile phones in the world today. GSM phones can operate in three or four different frequency bands including cellular and PCS bands. This flexibility allows subscribers to use their phones in many places around the world. GSM phones require SIM (Subscriber Identity Module) cards. These removable or interchangeable cards store a subscriber’s subscription information and allow users to change phones by simply switching the SIM card from one mobile phone to another or switching SIM cards on a single phone. The ability to switch SIM cards is currently blocked by carriers in the United States. See “Mobile Phone,” “Cell Phone,” “Cellular” and “Personal Communications Service (PCS).”


Mobile Phone


Mobile is the common term used outside of the United States and Canada to refer to wireless services or wireless phones. In the United States and Canada, the term Mobile Service is used by the telecommunications industry to refer to Improved Mobile Telephone Service (IMTS) which is a pre-cellular, low frequency VHF/UHF radio system. IMTS operates in low bands (35-44 MHz, 152-158 MHz and 454-460 MHz). Satellite, Cellular and PCS systems have replaced residential IMTS for most residential use. Some businesses still use IMTS radio systems to support their business. Today only a handful of exchanges and 1000-blocks are classified as Mobile. Exchanges classified as Mobile (NXX Type 01) are normally excluded from wireless frames. See “Cell Phone,” “Cellular,” “Personal Communications Service (PCS)” and “GSM.”













NXX Type


Neustar provides a variety of telephone numbering services to the telecommunications industry. They are currently the Number Portability Administrator and maintain the databases associated with ported numbers, the relationship between the number kept and the new switch to which that number has been ported. As the North American Numbering Plan Administrator, Neustar controls the assignment of area codes and prefixes, and as the National Pooling Administrator controls the assignment of thousand-blocks as required by thousand-block pooling.

Neustar maintains databases of all ported numbers: wireline (landline) to wireline, wireless (cellular) to wireless, wireline to wireless and wireless to wireline. The wireline to wireless database is critical in the process of identifying cellular telephone numbers within the landline RDD frame, especially given the number of people porting their home wireline telephone number to a cellular number continues to grow. These databases are updated daily and there is a license fee to access them.


NXX Type is a term and set of two-digit codes used by Telcordia and communications carriers to define the type of telephone service provided in an exchange or 1000-block. See “POTS,” “Cellular,” “Personal Communications Service,” “Shared Service,” “Special Billing” etc.

Personal Communications Service (PCS)

The name of the broadband wireless or cellular service that uses the 1850-1910 MHz and 1930-1990 MHz radio bands for digital mobile phone services in Canada and the United States. PCS services include both voice and advanced two-way data capabilities that are generally available on small, mobile multi-function devices. Code Division Multiple Access (CDMA) and GSM systems use the PCS frequencies.
The FCC set aside the frequency band of 1850-1990 MHz for mobile phone use in 1994, as the original cellular phone band at 800-894 MHz was becoming overcrowded. Sprint was the first company to set up a PCS network, a GSM-1900 network. Sprint upgraded to CDMA technology and sold their GSM infrastructure to Omnipoint, which later became part of T-Mobile USA. Today many broadband PCS licensees (including the major players (Sprint/Nextel, T-Mobile, Cingular/AT&T, US Cellular, and Verizon) offer PCS services in competition with existing cellular licensees.


Old Bellcore/Telcordia acronym for “Plain Old Telephone Service,” or telephone service carried over landlines as opposed to the airwaves (wireless).


Predictive Dialer


See “Autodialer.”




See “Telephone Number Components.”


Random Digit Dialing


A method of reducing sampling frame error that involves the use of randomly generated numbers for a telephone survey, instead of relying on telephone directories or other lists of numbers that may exclude certain types of consumers.


Shared Service


A Shared Service exchange or 1000-block is one in which the service provider may provide more than one type of service in that exchange or 1000-block. For example NXX Type “Shared POTS and Cellular” designates an exchange or 1000-block in which the service provider may be providing both POTS and cellular service.

Special Billing






Some exchanges and 1000-blocks have an NXX Type defined as “Special Billing.” According to Telcordia, “there may be line numbers or thousands blocks assigned to a Service Provider who has requested a Local Exchange Carrier Intra-LATA special billing option on a LATA-wide basis or on a SELECTIVE exchange basis.”

These special cases appear to involve areas where Intra-LATAs calls may cross state lines and may therefore require special billing procedures.

See “Telephone Number Components.”


Telephone Number Components


Telephone Number Components:

North American Numbering Plan is the integrated telephone numbering plan covering the United States and its territories, Canada, Bermuda, and 16 Caribbean nations. It is a system of three-digit numbers.



Area Code is the term associated with the first three digits of a 10-digit telephone number that allows communications networks to direct telephone calls to particular regions on the network where they are further routed to local networks. It is also known as the NPA or Numbering Plan Area. An area code can cover an entire state or a city or part of a city. In certain areas of the plan, multiple area codes can service the same area (overlays).

Prefix is the term associated with the second set of three digits of a 10-digit telephone number. This set of numbers allows communications networks to direct calls to more local areas within the larger area code. Each prefix has been assigned to a single Telephone Operating Company, a company that has been licensed by the FCC to provide telecommunications services over the Public Switched Telephone Network. Every prefix has 10,000 possible phone number combinations (0000-9999).

Suffix is the term associated with the final four digits of a 10-digit telephone number. This set of numbers allows communications networks to direct calls to the switch associated with the end user. The suffix can be further segmented into blocks or banks of consecutive numbers.

1000-blocks or 1000-banks are blocks of 1,000 consecutive suffix numbers starting with the same digit (0000-0999). Within a prefix, 1000-blocks can be assigned to telephone operating companies other than the company responsible for the prefix.

100-blocks or 100-banks are blocks of 100 consecutive suffix numbers starting with the same two digits (1100-1199). Analysis of listed telephone numbers in 100-blocks is used to create list-assisted telephone frames.



Exchange is a term that is frequently used in place of the term prefix, but an exchange is actually the geographic area serviced by a prefix or set of prefixes. For , 203-929 and 203-926 are two of the many prefixes that service the Huntington, Conn., exchange area. Prefixes are numbers, but exchanges are usually associated with a place name such as Huntington, Conn. Exchanges usually have a single building where all the wires in all the prefixes come together and from which calls are directed to and from users in those prefixes. A set of geographic coordinates associated with this building have traditionally been used to determine calling areas and the cost of making a phone call (local vs. long distance). For this reason, exchanges are sometimes referred to as Billing Centers or Rate Centers or Wire Centers. In prefixes that have multiple service providers and different types of service (POTS+cellular+broadband) individual 1000 blocks may have place names and rate center coordinates that are different from those associated with the prefix.


Text Messaging






A telecommunications protocol that allows the sending of "short" (160 characters or less) text messages, person-to-person messaging. It is available on most digital mobile phones and some personal digital assistants with wireless telecommunications. The individual messages that are sent are called text messages, SMSes, texts or txts.

Voice over Internet Protocol. VoIP providers basically reroute phone calls over the internet. VoIP service (cable, DSL, etc.) is still primarily landline service and VoIP numbers are normally assigned in landline prefixes. VoIP companies provide a special modem connected to the internet into which the subscribers plug a regular landline phone. Some wireless carriers offer VoIP using a specially equipped cell phone assigned a number from their set of cellular prefixes. Thus it appears that VoIP is not a separate mode but can be incorporated in either service. 

Subscribers can keep their existing phone number and switch it to VoIP (i.e. port their number). Under certain circumstances they may be able to keep their VoIP number when moving to a different area code and get an in-bound telephone number from a different area code through the use of what is commonly referred to as a virtual phone number. Thus there is a potential loss in geographic precision that is also characteristic of cell phone numbers without VoIP. Not all VoIP providers allow their subscribers to “list” their telephone number in a directory or make their telephone number available through Directory Assistance. This means that list-assisted RDD may underrepresent exchanges and 1000-blocks assigned to VoIP services.

At the moment there are no indications of subscribers treating their VoIP phone differently than they would treat a landline or cellular phone. For this reason VoIP numbers can be dialed as regular landline or cell numbers.


Is a telephone connection where communications travel through the airwaves rather than over wire or fiber optic cable. This term is regularly used in the telecommunications industry, particularly by government agencies, when referring to non-landline telephone service and includes cellular, PCS, Mobile and Paging services.  See “Cellular” and “Cell Phone,” “Mobile Phone,” “Personal Communications Service (PCS)” and “GSM.”




Synonymous with “landline”. Is regularly used in the telecommunications industry, particularly by government agencies, when referring to landline telephone service.


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