a central office or other location where connections between telephone lines are made (originally by a switchboard operator, now usually…

the nearest telephone exchange to which a particular telephone is connected.

an establishment where members of the public can make and receive telephone calls.

U.S. A (central) telephone exchange. Also: an operator at such an exchange. Often without determiner. Now historical.

= telephone exchange n. at telephone, n. compounds 3.

an exchange on private premises by which private lines may be connected to a public network; abbreviated PBX.

private branch exchange.

an exchange which acts as a main switching centre in an area containing a number of exchange groups.