Vigor3300 Series User’s Guide
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3300V has two expansion slots; each slot can be plugged into one 4-port VoIP card. The VoIP
card involves two kinds of interface: FXS and FXO. You can deploy different VoIP
applications according to the requirements.
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FXS (Foreign eXchange Station) and FXO (Foreign eXchange Office) are assembled with a
pair. A telecommunications line from an FXO device must be connected to an FXS device.
Similarly, an FXS device must be connected to an FXO device. For example, PSTN is FXS
equipment, and a telephone is FXO equipment.
