The telephone doesn't ring with a FXS connection.The telephone needs to be a POT's phone or a 2500 handset .
The RSG light needs to come on then off indicating that the local interface FXS should be ringing.
Ring voltage may not be turned up all the way. On the power supply there is a potentiometer that controls the ring voltage. It is a blue square potentiometer with a white dial in the center, located towards the back of the mux on the power supply card. For maximum voltage to the FXS connection you must turn this POT clockwise .
Make sure that the phone used has the ringer set to " loud " .