Abstract: A transducer for indicating the percentage filling of an underground mine storage bunker. The contents of the bunker is proportional to the rotation of a shaft of a conveyor which feeds it. The transducer comprises a shaft encoder for sensing this rotation and derives a signal indicative thereof. The signal is fed to a circuitry which includes a visual display for a further signal derived in the circuitry which is equal to the first mentioned signal and a bunker full warning light which is energized when the further signal exceeds a preselected value. The circuitry is compatible with a varied range of input signals.