The BK-380, BK-390 bistable contact is a magnetically operated changeover switch which permanently changes its electrical operating status depending on the direction of movement of a passing magnet system. It can be used on level indicators, e.g. W-35... water level indicat-ors, MTA-50 tank level indicators, ÜTA-32... raised tank indicators, etc., for realizing or retrofitting a level control system.