 Tustin, who did most of the design work, found that the system had a large time constant, due to the inductance of the field windings.In order to improve its response, he supplied the field windings with a constant current, and used a partially compensated Metadyne to control the armature current of each motor.Tustin compared Ward Leonard control systems, Metadynes and Amplidynes, and accepted that each had its merits, but favoured the Metadyne, of which he had several years experience from their use in traction control.