BORGWARNER AUTOMOTIVE INC., CHICAGO, ILL. Direct sensing technology (DST) and electronic direct sensing technology (EDST) fan drives are said by the manufacturer to provide reliable variable-speed cooling for engines with limited air flow, such as rear engine transit buses, concrete mixers, and off-highway equipment. The fan drives respond directly to temperature changes in engine coolant, charge air, engine oil, transmission fluid, and hydraulic oil. DSTs are air actuated, using a temperature-sensing pressure regulator valve located in the cooling water jacket to generate a variable air pressure signal. EDSTs use an electrical signal directly from the engine ECM, which commands the fan to run at the speeds required to maintain proper coolant, oil, and charge air temperatures.