 Unlike Rosenberg's solution, Pestarini, who later became a Professor at the Institute Electrotechnico Nazionale Galileo Ferraris in Turin, connected the additional brushes to an external supply to produce a transformer metadyne.The machine worked as a voltage-to-current amplifier because the flux generated by the current to the load opposed the flux in the control circuit.Development work at Metropolitan-Vickers in the 1930s was led by Arnold Tustin, and the company held the British patents for the Metadyne.