KOBOLD limit switches of model NEW are used for level monitoring and pump control of conductive liquids. The design without any moving parts also allows service with critical media with, for example, solid content, negligible density or high viscosity. The instruments operate on the conductive principle. A low a. c. voltage is applied between the earth electrode and a switching point electrode. The a. c. voltage is electrically isolated from the mains for safety reasons. If the conductive medium touches the electrodes, a negligible alternating current flows across the electrodes and the conductive medium to the electrode relay. The relay amplifies the alternating current and operates a switching relay or a pump controller.