Answer #1

FXO stands for Foreign Exchange Office and FXS denotes Foreign Exchange Subscriber. These two terms are used when talking about analogue telephones. In general, FXS is described like a wall plug, whilst FXO is seen as a phone plug. Find other detailed differences here below.

1. Dial tone
A prominent difference that is seen between these two terms is that FXS works by providing the dial tone, but FXO is the one that requests the dial tone. This means FXS offers the loop current, ringing voltage and dial battery. However, FXO receives the touch tone numbers.

2. Mode of working
The FXO functions by receiving the regular POTS service from the PSTN. As such, the FXO is regarded to be mainly directed towards a Telecom office. Off-hook and on-hook indication changed the main services offered by FXO interfaces to network devices. Conversely, FXS delivers PTSN from a certain telephone company and it therefore requires being connected to either a modem or telephone. It is mainly directed.

3. Services offered
The services offered by both aforementioned terms differ since an FXO device connects to a certain office, but FXS devices connect to stations. Furthermore, FXS is generally directed at all telephone subscribers. The main services any FXS interface offers include battery current, dial tone and ring voltage. However, FXO offers the vital service of initiating a call and FXS is the one responsible for receiving the call. FXS therefore indicates when calls are going to be routed.

4. Power
FXS devices supply close to 50V DC power. This means during any crisis, FXO devices will use the other FXS lines for power. This allows it to still remain operable in times of power failure.

In short, FXS offers the dial tone after FXO has requested it. Furthermore, FXO works by initiating the call and FXS is responsible for receiving the call.

Answered By: daniel [554 ]