The new microcontroller based FKD331 is a multistage electronic capacity controller for multi cylinder reciprocating compressor or rack systems. LCD Based unit has easy to use settings, like Set point -Low pressure (LP), Neutral Zone (NZ) & Interstage timer. One Analog input (4 to 20mA) for pressure transmitter e.g. compressor suction or RTD Pt100 One Digital input (potential free) for compressor on feedback four/ six selay output for compressor capacity control solenoid valves and compressor trip adjustable neutral zone, time delay, calibration optional RS232/ RS485 port for communication optional available software for PC monitoring function capacity regulation. The cut-in capacity is controlled by signals from the connected pressure transmitter and the set reference. Outside the reference a neutral zone is set where the capacity will neither be cut in nor out. Outside the neutral zone the capacity will be cut in or out if the regulation registers a will take place with the set time delays. If the pressure however ‘approaches’ the neutral zone, the controller will make no changes of the cut-in capacity. Cut-in of steps are defined for either sequential or cyclic operation.