In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls. A central office (CO) is the physical building used to house inside plant equipment including telephone switches, which make telephone calls "work" in the sense of making connections and relaying the speech information.
The term exchange area can be used to refer to an area served by a particular switch, but is typically known as a rate center or wire center in the US telecommunications industry. (Local calling areas, in which it is not necessary to pay a long-distance rate, typically cover more than one rate center even in micropolitan and small metropolitan areas.) The exchange code or central office code (often called the prefix by the public) refers to the first three digits of the local number (NXX), though most non-rural exchanges have more than one code or prefix.
Wireless rate centers for mobile phones typically cover a much larger area than landline rate centers in urban and suburban areas, and often have dozens of codes of their own, in addition to those introduced on individual telephone numbers by local number portability (due to customers porting a cancelled landline to a wireless). It is sometimes confused with the area code (NPA), which covers multiple exchanges, and which an exchange can have more than one of due to overlays of new area codes. In the United States, local exchange areas together make up a legal entity called local access and transport areas (LATA) under the Modification of Final Judgment (MFJ).
Read more about Telephone Exchange: Historic Perspective, Technologies, Switch Design, Fault Tolerance, Internet Exchanges
Famous quotes containing the words telephone and/or exchange:
“It is possible that the telephone has been responsible for more business inefficiency than any other agency except laudanum.... In the old days when you wanted to get in touch with a man you wrote a note, sprinkled it with sand, and gave it to a man on horseback. It probably was delivered within half an hour, depending on how big a lunch the horse had had. But in these busy days of rush-rush-rush, it is sometimes a week before you can catch your man on the telephone.”
—Robert Benchley (1889–1945)
“We never exchange more than three words with a Friend in our lives on that level to which our thoughts and feelings almost habitually rise.”
—Henry David Thoreau (1817–1862)