Fob detectors are an important part of any keg beer dispense system.
Fob detectors operate when a keg runs out and shut down the line to prevent it creating wasteful frothing or fobbing.
Where excess fob or froth has been generated this is removed by depressing the spring loaded vent button on the top of the fob detector, exhausting the excess gas which has caused the frothing.
Just as soon as the fob detector fills with beer again you can resume serving.
It is highly recommended that each of your keg beer lines be fitted with a fob detector.