FXO vs. FXS

There is a lot of confusion about analog cards, modules, and signalling.

Here is an explanation:

FXO = Foreign eXchange Office.  These are typically 'devices' like analog phones or fax machines.

FXS = Foreign eXchange Station.  This is the medium for analog transmission (i.e. phone lines).

Now the confusion!  The module that is inserted within the Sangoma A200D analog card is OPPOSITE the type of device you connect to it.

FXO modules create FXS signalling.  So you plug analog lines into FXO ports.

FXS modules create FXO signalling.  So you plug analog phones into FXS ports.

Yes the opposite nature of the nomenclature is confusing.

Best practices: talk to the customer in terms of what they are going to connect to the port.

Are you going to plug in an analog phone/fax machine or an analog line?

You can use this page for reference.  Don't confuse the customer by trying to explain the equal-but-opposite madness of the Telco world.

This command will show you which modules are inserted into the Sangoma A200 Shark card and any Remora cards.

This A200 has two different modules in it.  One FXO and one FXS.  This server can accept two analog lines and two analog devices.