BLC101 is a low-cost electronic level controller available for DIN-rail and panel mounting. It employs measurement of the electrical conductivity of the liquid between electrodes or between electrode and metal vessel case and is applicable for liquids with relatively high conductivity that are normally used in chemical, paper, food, wine, biotechnological industries, etc. BLC101 can monitor 1, 2, or 3 fixed levels, and a corresponding relay is activated or deactivated when each level is reached (drainage / supply control). Besides signaling reached level, the output relays may also be used for controlling electrical actuators. The direction of relay action at reached level as well as the connection (dependence) between levels is user-selectable. The device can also be configured as a drainage or supply level controller with alarm relay. A high-tech microprocessor circuit guarantees accuracy and stability, prevents electrolytic polarization, and ensures stable operation. A possibility to adjust output activation threshold as well as an LED indication makes the BLC101 level controller a solution for a wide range of level related problems.