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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 is a set of digits forming the most-significant part of the dialing sequence to reach a telephone subscriber.
Either type of class-4 switch might be referred to as a "toll switch." These terms were used because long-distance, or "toll," calls had to pass through class-4 switches, where the billing for the calls would be handled. Class-4 switches at that time often had an associated Traffic Service Position System (TSPS) to handle operator-assisted ...
Signalling System No. 7 (SS7) is a set of telephony signaling protocols developed in the 1970s that is used to setup and teardown telephone calls on most parts of the global public switched telephone network (PSTN). The protocol also performs number translation, local number portability, prepaid billing, Short Message Service (SMS), and other ...
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 the subscriber number, which might consist of the code for a particular telephone exchange.
Additional features, such as billing equipment, may also be incorporated into the exchange. The Bell System dial service implemented a feature called automatic number identification (ANI) which facilitated services like automated billing, toll-free 800-numbers, and 9-1-1 service. In manual service, the operator knows where a call is originating ...
Some geographic area codes are similar to the toll-free codes, e.g., 801, 818, 860. Toll-free numbers are also sometimes confused with 900-numbers, for which the telephone company bills the callers at rates far in excess of long-distance service rates for services such as recorded information or live chat.
PK 201 (PSTN Switch with R1 register signaling, not widely used) PK 202 (PSTN Switch with R2 register signaling, very frequently used in 80's) UK 101, UK 102 (PBXes up to 23 and 57 lines) UK 111, UK 112 (PBXes of higher capacities, expandable to thousands of lines)
E.164 is an international standard (ITU-T Recommendation), titled The international public telecommunication numbering plan, that defines a numbering plan for the worldwide public switched telephone network (PSTN) and some other data networks.