Foreign exchange office

From Wikipedia, the free encyclopedia

A Foreign Exchange Office, or FXO, is a telephone interface that receives POTS, or Plain old telephone service. It generates the on-hook and off-hook indicators used to signal a loop closure at the FXO's end of the circuit. Analog telephone handsets, fax machines and (analogue) modems are FXO devices. FXO interfaces are also available for computers and networking equipment to allow these to interact directly with POTS systems. These are commonly found in devices acting as gateways between VoIP systems and the PSTN. The TDM400P is one such card.

The FXO must be connected to the Foreign exchange station interface, or FXS interface. The FXS interface delivers the familiar dial tone and ring tone to the FXO and supplies the power for the FXO device to work.

[edit] In a nutshell

FXO is any device that, from the point of view of a telephone exchange, seems to be a regular telephone. As such, it should be able to accept ring signals, go on-hook and off-hook, and send and receive voice signals.