Foreign eXchange Office
(FXO) An analog telephone plug on a handset that receives POTS service from the telephone exchange ("central office") via a Foreign eXchange Subscriber socket and provides on-hook/off-hook indication to the exchange.
Last updated: 2008-01-17
foreground ♦ Foreign eXchange Office ♦ Foreign eXchange Subscriber
Try this search on Wikipedia, Wiktionary, Google, OneLook.