FXO Gateways connect your devices to an external phone line and provide Failover or Fallback functionality in the event of an internet outage or a network catastrophe.
AnFXO Gateway can be used to connect several POTS lines; the gateways are typically available in 1, 2, 4, and 8-port versions.
The port that accepts the analogue line is the FXO (Foreign Exchange Office).It's the phone or fax machine plug, as well as the plug(s) on your analogue phone system. It sends out an on-hook/off-hook signal (loop closure). The FXO port is often referred to as the "FXO device" because it is connected to a device such as a fax or a phone. This port establishes the analogue line connection (FXS).
DAG1000-4O FXO Analog Gateway is a type of access gateway offering seamless connectivity between IP-based telephony networks and legacy telephones (POTS) and PBX systems.