What is "telephone exchange"

exchange \ex*change"\ ([e^]ks*ch[=a]nj"), n. [OE. eschange, eschaunge, OF. eschange, fr. eschangier, F. ['e]changer, to exchange; pref. ex- out + F. changer. See Change, and cf. Excamb.]

1. The act of giving or taking one thing in return for another which is regarded as an equivalent; as, an exchange of cattle for grain.

2. The act of substituting one thing in the place of another; as, an exchange of grief for joy, or of a scepter for a sword, and the like; also, the act of giving and receiving reciprocally; as, an exchange of civilities or views.

3. The thing given or received in return; esp., a publication exchanged for another.
   --Shak.

4. (Com.) The process of setting accounts or debts between parties residing at a distance from each other, without the intervention of money, by exchanging orders or drafts, called bills of exchange. These may be drawn in one country and payable in another, in which case they are called foreign bills; or they may be drawn and made payable in the same country, in which case they are called inland bills. The term bill of exchange is often abbreviated into exchange; as, to buy or sell exchange.

   Note: A in London is creditor to B in New York, and C in London owes D in New York a like sum. A in London draws a bill of exchange on B in New York; C in London purchases the bill, by which A receives his debt due from B in New York. C transmits the bill to D in New York, who receives the amount from B.

5. (Law) A mutual grant of equal interests, the one in consideration of the other. Estates exchanged must be equal in quantity, as fee simple for fee simple.
   --Blackstone.

6. The place where the merchants, brokers, and bankers of a city meet at certain hours, to transact business; also, the institution which sets regulations and maintains the physical facilities of such a place; as, the New York Stock Exchange; a commodity exchange. In this sense the word was at one time often contracted to 'change

   Arbitration of exchange. See under Arbitration.

   Bill of exchange. See under Bill.

   Exchange broker. See under Broker.

   Par of exchange, the established value of the coin or standard of value of one country when expressed in the coin or standard of another, as the value of the pound sterling in the currency of France or the United States. The par of exchange rarely varies, and serves as a measure for the rise and fall of exchange that is affected by the demand and supply. Exchange is at par when, for example, a bill in New York, for the payment of one hundred pounds sterling in London, can be purchased for the sum. Exchange is in favor of a place when it can be purchased there at or above par.

   Telephone exchange, a central office in which the wires of any two telephones or telephone stations may be connected to permit conversation.

   Syn: Barter; dealing; trade; traffic; interchange.

Telephone exchange \Tel`e*phone ex*change"\ A central office in which the wires of telephones from local subscribers may be connected by switches to other local telephones or to long-distance lines, to permit transmission of conversation or data.

Note: In the late 1990's the traditional copper wires connecting local telephones to the telephone exchange have begun to be replaced with optical fiber connections.

n. 1 any equipment that establishes connections between telephones 2 the rooms housing such equipment

n. a workplace that serves as a telecommunications facility where lines from telephones can be connected together to permit communication [syn: central, exchange]

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. For business and billing purposes, telephony carriers also define rate centers, which in larger cities may be clusters of central offices, to define specified geographical locations for determining distance measurements.

In the United States and Canada, the Bell System established in the 1940s a uniform system of identifying central offices with a three-digit central office code, that was used as a prefix to subscriber telephone numbers. All central offices within a larger region, typically aggregated by state, were assigned a common numbering plan area code. With the development of international and transoceanic telephone trunks, especially driven by direct customer dialing, similar efforts of systematic organization of the telephone networks occurred in many countries in the mid-20th century.

For corporate or enterprise use, a private telephone exchange is often referred to as a private branch exchange (PBX), when it has connections to the public switched telephone network. A PBX is installed in enterprise facilities, typically collocated with large office spaces or within an organizational campus to serve the local private telephone system and any private leased line circuits. Smaller installations might deploy a PBX or key telephone system in the office of a receptionist.