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A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing. It is used when initiating a telephone call to transmit the destination telephone number to a telephone exchange .
The most commonly used telephone sets for the 1A2 systems were modifications of the Bell System standard 500-series telephones for rotary dial systems, and the 2500-series Touch-Tone desk sets. For key system operation these sets were equipped with a set of push-buttons ( keys ) and additional internal contact springs to control the additional ...
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 replaced rotary dialing , that had been developed for ...
The telegraph keys or telephone dial creates trains of on-off current pulses corresponding to the digits 1–9, and 0 (which sends 10 pulses). This equipment originally consisted of two telegraph keys engaged by knife switches, and evolved into the rotary dial telephone. The central office switching equipment has a two-motion stepping switch. A ...
The rotary machine switching system, or most commonly known as the rotary system, was a type of automatic telephone exchange manufactured and used primarily in Europe from the 1910s. The system was developed and tested by AT&T's American engineering division, Western Electric , in the United States, at the same time when Western Electric was ...
A typical Western Electric hand telephone set of c. 1930. It consists of a handset mounting with the handset held in a cradle, and a subscriber set mounted against a wall or vertical surface in close proximity. Shown is a B1A hand telephone set, also known as the type 102B-3 hand telephone set.
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.
A typical rotary-dial key telephone: the Western Electric eighteen-button Call Director, manufactured from 1958 to the early 1980s. Before the development of large-scale integrated circuits, key systems typically consisted of electromechanical components, such as relays, as were larger telephone switching systems.