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Telephone numbers listed in 1920 in New York City having three-letter exchange prefixes. In the United States, the most-populous cities, such as New York City, Philadelphia, Boston, and Chicago, initially implemented dial service with telephone numbers consisting of three letters and four digits (3L-4N) according to a system developed by W. G. Blauvelt of AT&T in 1917. [1]
A subscriber would call 950-XXXX to reach a specific carrier, then dial the long-distance destination number. This feature group 'B' has been rendered obsolete by 1010xxx "dial-around" feature group 'D', but the exchange remains reserved in each individual area code. 951
Toll-free telephone numbers in the North American Numbering Plan have the area code prefix 800, 833, 844, 855, 866, 877, and 888. Additionally, area codes 822, 880 through 887, and 889 are reserved for toll-free use in the future. 811 is excluded because it is a special dialing code in the group NXX for various other purposes.
All-number calling was a telephone numbering plan introduced in 1958, [35] that converted telephone numbers with exchange names to a numeric representation of seven digits. The original plan of 1947 had been projected to be usable beyond the year 2000. However, by the late 1950s it became apparent that it would be outgrown by about 1975. [36]
A telephone prefix is the first set of digits after the country, and area codes of a telephone number.In the North American Numbering Plan countries (country code 1), it is the first three digits of a seven-digit local phone number, the second three digits of the 3-3-4 scheme.
Phone numbers whose exchanges begin with 1 are also occasionally used as fictional numbers. Under the North American Numbering Plan, all telephone exchanges run from 200 to 999 with similar restrictions on telephone area codes.
Here is a list of scammer phone numbers that are known by government agencies such as the Federal Trade Commission. Quick Take: List of Scam Area Codes.
A telephone exchange, also known as a telephone switch or central office, is a crucial component in the public switched telephone network (PSTN) or large enterprise telecommunications systems. It facilitates the interconnection of telephone subscriber lines or digital system virtual circuits, enabling telephone calls between subscribers.