FXS and FXO are telecom abbreviations used to describe physical premise connectivity interfaces.
FXS – stands for Foreign Exchange Subscriber – these ports provide dial-tone connectivity for analog telephones, analog conference phones, modems, dialers and other analog devices or interfaces that require access to your PBX or IP-PBX.
These are physical ports that provide current, and scalability may depend on the system being used.
In VoIP deployments, ATA ( Analog Terminal Adapters) are used to convert analog-to-ethernet and deliver FXS interface anywhere withing the IP networks.
FXO – stands for Foreign Exchange Office – these are also physical ports, that allow TelCo analog lines to be connected to the PBX or IP-PBX. These ports respond to levels of current on the incoming line and open up connectivity for the telephone system to handle the call. In VoIP deployments, FXO Gateways, that convert analog-to-ethernet to accomodate TelCo Lines.
For example: a company in Boston, Mass., wants to have their local customers in London, UK to dial a local telephone number and connect to an agent in Boston. See Diagram Below.
