What are FXO and FXS port?

Posted on 2009-04-25
Last Modified: 2013-12-27
What are FXO and FXS port?
Question by:davidlu766
    LVL 4

    Accepted Solution

    FXS and FXO are the name of ports used by Ananlog phones.FXS (Foreign eXchange Subscriber interface) is the basic connection port that you see at your home for connecting the RJ11 Jack of the phone. This port provides the dialtone, small current and voltage to the phone line.

    FXO (Foreign eXchange Office) is that port that you see on the telephonic devices like the Phone, Fax etc. from where a cable is plgged in and the other end is plugged into the FXS jack on the wall.
    So in short you can say that FXS is the the plug on the wall where as FXO is the plug on the phone.

    Author Comment

    So, both uses RJ11 ports?
    LVL 4

    Expert Comment

    Yes, definately.
    LVL 4

    Expert Comment

    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
    LVL 32

    Expert Comment


    FXO is the outside line, the outside POTS line,

    FXS is the port that connects your phones.

    harbor235 ;}
    LVL 79

    Expert Comment

    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

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