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  • Telephone exchange


    telephone operator manually connecting calls with cord pairs at a telephone switchboard. A modern central office, equipped for voice communication and broadband data. A telephone exchange is a telecommunications system used in the public switched telephone network or in large enterprises. An exchange consists of electronic components and in older systems also human operators that interconnect (switch) telephone subscriber lines or virtual circuits of digital systems to establish telephone calls between subscribers. In historical perspective, telecommunication terms have been used with different semantics over time. The term telephone exchange is often used synonymously with central office (CO), a Bell System term. Often, a central office is defined as a building used to house the inside plant equipment of potentially several telephone exchanges, each serving a certain geographical area. Such an area has also been referred to as the exchange. Central office locations may also be identified in North America as wire centers, designating a facility from which a telephone obtains dial tone.

  • Electronic Yellow Pages


    Electronic Yellow Pages are online versions of traditional printed business directories produced by telephone companies around the world. Typical functionalities of online yellow pages include the alphabetical listings of businesses and search functionality of the business database by name, business or location. Since Electronic Yellow Pages are not limited by space considerations, they often contain far more comprehensive business information such as vicinity maps, company profiles, product information, and more. An advantage of Electronic Yellow Pages is that they can be updated in real time; therefore, listed businesses are not constrained by once-a-year publishing of the printed version which leads to greater accuracy of the listings since contact information may change at any time. Before the popularity of the internet, business telephone numbers in the United Kingdom could be searched by accessing a remote computer terminal by modem. The initial prototype of this was superseded in 1990 with a commercial service.

  • List of yellow pages



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