VoIP connectivity into a new or existing environment can happen in a few ways by using different types of VoIP Gateways.
If you are researching into deploying a VoIP Telephony System on your own for the first time, you are probably seeing FXS and FXO acronyms all over the place. If you haven?t figured it out yet, this can be very frustrating. Maybe this will help you make sense of it all.
FXS ? According to Wikipedia, FXS stands for foreign exchange station. FXS is a port that connects internally to an office phone or PBX. Think of the S as meaning a station.
FXO ? According to Wikipedia, foreign exchange office designates a telephone signaling interface that receives POTS (plain old telephone service). FXO is a port that will connect a device to an outside telephone line.
The FXS port connects the telephone or PBX to the Gateway, which connects to the internet via a Router or modem. Some Gateways or ATA?s also have an FXO port. This provides fail-over in which case, in the event of internet failure, you can still make telephone calls via the POTS line.
FXO ports are most often used on Gateways and PBX?s to support Fail-over or Fallback as mentioned above. Most critical phone systems should have a fail-over feature so phone calls or faxes may continue in the event of internet failure.