Abstract: An induction regulator valve is incorporated in the induction manifold of a compressor to provide for infinitely variable regulation of the output from the rotary type compressor, in particular the screw-type compressor. The closing piece of the induction regulator valve can be adjusted by means of an actuator system. To improve this regulation performance of this system, in particular to reduce its sensitivity when the regulator valve is almost closed, the spring system is formed so that its stiffness varies along the length of its spring path, the stiffness of the spring system being smaller when the induction regulator valve is open than when it approaches the closed position of the closing piece of the induction regulator valve.