Frequently Asked Questions
What do the terms FXS and FXO stand for?
Last Updated 6 years ago
- FXS and FXO are the name of ports used by Analog phone lines (also known as POTS - Plain Old Telephone Service).
- FXS - Foreign exchange Subscriber interface is the port that actually delivers the analog line to the subscriber. In other words it is the ‘plug on the wall’ that delivers a dial tone, battery current and ring voltage.
- FXO - Foreign exchange Office interface is the port that receives the analog line. It is the plug on the phone or fax machine, or the plug (s) on your analog phone system. It delivers an on-hook/off-hook indication (loop closure). Since the FXO port is attached to a device, such as a fax or phone, the device is often called the ‘FXO device’.