The FE ports available on some Sensor models failopen and require no extra hardware; simply connect your cables to a port pair (For example, 1A-1B).
Fail-closed mode for FE ports requires use of the fail-closed dongles on each connecting cable of the port pair. The fail-closed dongles provided with the Sensor are designed to complement 10/100 monitoring port functionality. You plug the dongles into a Sensor's 10/100 monitoring port, and then connect a Cat 5/Cat 5e cable to the dongles.