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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 – this ...
All-number calling. All-number calling (ANC) is a telephone numbering plan that was introduced into the North American Numbering Plan by the Bell System in the United States starting in 1958 [1] to replace the previous system of using a telephone exchange name as the first part of a telephone number. [2] The plan prescribed the format of a ...
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 vertical service code (VSC) is a sequence of digits and the signals star (*) and pound/hash (#) dialed on a telephone keypad or rotary dial to access certain telephone service features. [1] Some vertical service codes require dialing of a telephone number after the code sequence. On a touch tone telephone, the codes are usually initiated with ...
www.itu.int /rec /T-REC-Q.23 /en. Dual-tone multi-frequency signaling (DTMF) is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers. [ 1 ] DTMF was first developed in the Bell System in the United States, and became known ...
DTMF keypad layout. Introduced to the public in 1963 by AT&T, Touch-Tone dialing greatly shortened the time of initiating a telephone call.It also enabled direct signaling from a telephone across the long-distance network using audio-frequency tones, which was impossible with the rotary dials that generated digital direct current pulses that had to be decoded by the local central office.
This is a list of international dialing prefixes used in various countries for direct dialing of international telephone calls.These prefixes are typically required only when dialling from a landline, while in GSM-compliant mobile phone (cell phone) systems, only the symbol + before the country code may be used [citation needed] irrespective of where the telephone is used at that moment; the ...
A telephone number 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.