NationMaster - Encyclopedia: Rotary dial

The rotary dial is a device mounted on or in a telephone or switchboard that is designed to send interrupted electrical pulses, known as pulse dialing, corresponding to the number dialed. It was invented in 1888 by Almon Strowger. The device was phased out from the 1970s onwards with the onset of Touch Tone dialing, which uses a telephone keypad instead of a dial. Some telephone systems no longer recognize pulse dialing by default, so now it would have to be ordered from the telephone company as a special feature, to support older customer equipment. Image File history File linksMetadata No higher resolution available. ... Image File history File linksMetadata No higher resolution available. ... This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... Telephone switchboard, 1974 A switchboard (also called a manual branch exchange) is a device used to manually connect a group of telephones from one to another or to an outside connection. ... In signal processing, the term pulse has the following meanings: A rapid, transient change in the amplitude of a signal from a baseline value to a higher or lower value, followed by a rapid return to the baseline value. ... Pulse dialing or loop disconnect dialing, also called Rotary or Decadic dialing in the United Kingdom (because up to 10 pulses are sent), is pulsing in which a direct-current pulse train is produced by interrupting a steady signal according to a fixed or formatted code for each digit and... Almon Brown Strowger (1839 â€“ May 26, 1902) gave his name to the electromechanical telephone exchange technology that his invention and patent inspired. ... The 1970s decade refers to the years from 1970 to 1979. ... A DTMF telephone keypad Dual-tone multi-frequency (DTMF) signaling is used for telephone signaling over the line in the voice-frequency band to the call switching center. ... A standard modern telephone keypad, as used for text messaging. ...

Form

The dial is circular. In its most common form, the dial is about 78 mm (3 inches) in diameter. Ten finger holes are cut through its outer perimeter. The dial is mounted via a shaft extending from inside the telephone or mounting and sits approximately 6 mm (¼ inch) above a faceplate. The faceplate is set so that through each finger hole, letters and numbers printed on the faceplate may be seen. In North America, traditional dials have letter codes displayed with the numbers under the finger holes in the following pattern: 1, 2 ABC, 3 DEF, 4 GHI, 5 JKL, 6 MNO, 7 PRS, 8 TUV, 9 WXY, and 0 Operator. However, such letter codes were not used in all countries. Older Australian rotary dial telephones also had letters, but the combinations were often printed in the center plate adjacent to the number. The 1 is normally set at approximately 60 degrees clockwise from the uppermost point of the dial, or approximately at the 2 o'clock position on a clock face, and then the numbers progress upward counterclockwise, with the 0 being at about 5 o'clock. A curved device called a finger stop sits above the dial at the 4 o'clock position. A millimetre (American spelling: millimeter, symbol mm) is an SI unit of length that is equal to one thousandth of a metre. ... An inch (plural: inches; symbol or abbreviation: in or, sometimes, â€³ - a double prime) is the name of a unit of length in a number of different systems, including English units, Imperial units, and United States customary units. ... An area code is officially known as a Numbering Plan Area (NPA). ...

Function

To dial a number, the user puts a finger in the corresponding finger hole and rotates the dial clockwise until it reaches the finger stop. The user then pulls out the finger, and a spring in the dial returns it to the resting position. For example, if the user dials "6" on a North American telephone, as the dial returns, electrical contacts wired through the mechanism underneath will open and close six times, thus sending six pulses to the central office. World map showing North America A satellite composite image of North America. ...

Early dials worked by direct or forward action. The pulses went out as the dial went around to the finger stop. When the user's hand motion was not smooth, it produced wrong numbers. In the late 1800s the dial was refined to be operated by a recoil spring and centrifugal governor. The user selects the digit to be dialed, rotates the dial to the finger stop, then releases it. The spring causes the dial to return to its rest position and the governor regulates the dialing pulses at its design rate, usually approximately 10 per second, sometimes as much as 20 pps. The rotary dial governor is subject to wear and aging, and may require periodic cleaning, lubrication and adjustment by a telephone technician. Modern electronic telephones that feature selectable pulse or tone dialing eliminate this maintenance chore. A centrifugal governor is a specific type of governor that controls the speed of an engine by regulating the amount of fuel admitted, so as to maintain a near constant speed whatever the load or fuel supply conditions. ...

Some telephones include a much smaller dial inside the handset, with a movable finger stop. The user rotates the dial clockwise until the finger stop ceases moving, then releases both. In this setting, there is no section of the rotating dial plate without holes, allowing a smaller dial diameter. This was introduced by Western Electric on the compact Trimline telephone, the first to locate the dial in the handset. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Company Masthead Logo Logo until circa 1969, also current logo on company web site Logo 1969-1983 Western Electric (sometimes abbreviated WE and WECo) was an American electrical engineering company, the manufacturing arm of AT&T from 1881 to 1995. ... A 220 Trimline rotary desk phone, showing the innovative dial with moving thumbstop The Western Electric Trimline telephone, aka The Manhattan, is a variety of telephone set designed by Henry Dreyfuss Associates for the Bell System (AT&T). ...

Different pulse systems are used, varying from country to country. For example, Sweden uses one pulse to signal the number zero, and 10 pulses to signal the number nine. New Zealand uses ten pulses minus the number desired; so dialling 7 produces three pulses. In Norway, the North American system with the number 1 corresponding to one pulse was used, except from the capital, Oslo, which used the same "inverse" system as in New Zealand. For this reason, the numbers on the dial are shifted in different countries, or even in different areas of one country, to work with their system because of the difference of the number arrangement on the dial. A relic of this system is found in differing emergency telephone numbers; the United Kingdom selected 999 due to the ease of converting call office dials to make free calls ('0' for the Operator was already free), whereas in New Zealand 1-1-1 was selected for the same reason (111 actually pulses 999 to the central office/telephone exchange). County District Viken Municipality NO-0301 Administrative centre Oslo Mayor (2004) Per Ditlev-Simonsen (H) Official language form BokmÃ¥l Area - Total - Land - Percentage Ranked 224 454 kmÂ² 426 kmÂ² 0. ... Many countries public telephone networks have a single emergency telephone number, sometimes known as the universal emergency telephone number or occasionally the emergency services number, that allows a caller to contact local emergency services for assistance. ... 999 is the United Kingdoms and Irelands emergency telephone number and Polands medical emergency number. ... 111 has been the emergency telephone number in New Zealand since September 1958. ...

Rotary dial telephones in the U.S. were sometimes equipped with apparatus blanks — a piece of plastic or metal blocking the opening in the telephone's housing — in place of a dial. In the Bell System, these telephones were referred to as non-dial. The most common applications for non-dial telephones were on Automatic ringdown circuits or manual service. Motto: (Out Of Many, One) (traditional) In God We Trust (1956 to date) Anthem: The Star-Spangled Banner Capital Washington D.C. Largest city New York City None at federal level (English de facto) Government Federal constitutional republic - President George Walker Bush (R) - Vice President Dick Cheney (R) Independence from... Ringdown: In telephony, a method of signaling an operator in which telephone ringing current is sent over the line to operate a lamp or cause the operation of a self-locking relay known as a drop. ... A telephone operator manually connecting calls with patch cables at a telephone switchboard. ...

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