What are FXO and FXS port?

So, both uses RJ11 ports?

Yes, definately.

FXO = Office you connect your line on it
FXS = Station you connect a phone set on it

Generally FXS board need a power supply (same as for internal disk drive) because ring need a burst of power to make your phone ringing. While FXO do not need to be powered.

Denis DIDIER
SR20 Service / France

FXO is the outside line, the outside POTS line,


FXS is the port that connects your phones.

harbor235 ;}

I like to think of it as where the dialtone comes from
FXO port - gets dialtone from the analog phone jack on the wall. FXO ports take incomming and make outgoing calls to outside lines possible.
FXS port - provides dialtone and ring voltage from the router to the phone device - fax machine, analog phone

If you plug an analog phone into a FXO port, you will not get dialtone or be able to make a call
If you plug a cable between a FXS port and the jack on the wall, you will not be able to make any calls


Yes, they both use standard telephone Rj11 jacks