FXO (Foreign Exchange Office) The Analog Trunk FXO is an interface that connects to a trunk line, like the one from your service provider to the IP telephony system. It receives ringing voltage and battery from FXS devices. FXO interfaces are used to connect IPPBX to the PSTN. One FXO channel is required for each line you receive from your telco. The module serve as the interface to connect the analog to VoIP system , here being Zycoo PBX.

The 4FXO module have four RJ11 port and can be slide to one of the module slot in office IPPBX like U50,U100 ,U80 The loop start Analog Interface provides the following features:

- Detects ringing when on-hook

- Detects loop current when off-hook

- Detects when tip/ring voltage crosses a set voltage when on-hook or off-hook (called DC triggering)

- Can accommodate private branch exchange (PBX) with –48V battery voltage