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Telephone numbers are of variable length. Local numbers are supported from landlines. Numbers can be dialled with a '0'-lead prefix that denotes either a geographical region or another service. Mobile phone numbers have distinct prefixes that are not geographic, and are portable between providers.
Fictitious numbers in (011x) and (01x1) area codes mostly end with the digits 496 0xxx, however Tyneside uses (0191) 498 0xxx. London uses 020 7946 0xxx; Cardiff uses 029 2018 0xxx; and Northern Ireland now uses 028 9649 6xxx after a previously reserved range was allocated for actual use.
Such numbers are an alternative to the traditional 'landline' numbers that are assigned geographically using a system of location-specific area codes. Non-geographic numbers are used for various reasons, from providing flexible routing of incoming phone calls to generating revenue for paid-for services.
However, generally they are considerably slower (typically by a factor 2–10) than fast, non-cryptographic random number generators. These include: Stream ciphers. Popular choices are Salsa20 or ChaCha (often with the number of rounds reduced to 8 for speed), ISAAC, HC-128 and RC4. Block ciphers in counter mode.
Personal numbering is the name for the virtual telephone number service in the UK. Typically the national destination code used for this service is (0)70 . The service provides a flexible virtual telephone number able to be routed to any other number, including international mobiles.
This is a list of telephone dialling codes in the United Kingdom, which adopts an open telephone numbering plan for its public switched telephone network. The national telephone numbering plan is maintained by Ofcom , an independent regulator and competition authority for the UK communications industries.
555 (telephone number) The telephone number prefix 555 is a central office code in the North American Numbering Plan, used as the leading part of a group of 10,000 telephone numbers, 555-XXXX, in each numbering plan area (NPA) (area code). It has traditionally been used only for the provision of directory assistance, when dialing NPA-555-1212.
Telephone numbers were displayed preceded by the exchange name, with the first three letters highlighted to indicate the code, and number, such as WHI tehall 1212 . Director schemes were gradually introduced in other major cities of the UK — Birmingham, Edinburgh, Glasgow, Liverpool and Manchester .
A telephone keypad using the ITU E.161 standard. A telephone keypad is a keypad installed on a push-button telephone or similar telecommunication device for dialing a telephone number. It was standardized when the dual-tone multi-frequency signaling (DTMF) system was developed in the Bell System in the United States in the 1960s that replaced ...
Telephone number mapping is a system of unifying the international telephone number system of the public switched telephone network with the Internet addressing and identification name spaces.