Status detection via current sensors, such as the occupancy detector LB101, has one crucial disadvantage: if the operating voltage is interrupted, so is the power supply. In this case, occupancy detection fails: the signal output will report unoccupied tracks that are, in fact, occupied. Power failures may be caused when the voltage is switched off or short circuits occur which are a frequent phenomenon in model railway systems. The voltage detector LB050 was designed to prevent faulty feedback. It checks whether digital voltage is applied to the track; if not, the present status will be fed back until voltage is reapplied.