Foreign eXchange Office

from The Free On-line Dictionary of Computing (8 July 2008)

Foreign eXchange Office
FXO

   <communications> (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.

   (2008-01-17)