Abstract: Apparatus for monitoring the level of a developing solution within a storage tank utilizing at least two electrodes having active surfaces exposed to the developing solution for the conduction of electrical current therebetween. The electrodes have their active surfaces positioned at different levels within the developing solution. One electrode serves as a reference and is always immersed in the developing solution. Electrical signals developed when the developing solution falls below the level of the active surface of the electrodes is utilized to trigger an electrical switching circuit which is connected to the electrodes for governing a signalling and/or control action of the developing station.