Abstract: A circuit for controlling operation of an electromagnet includes a source of voltage connectable to the electromagnet to produce current flow in one direction and develop a magnetic force therein. A dissipating circuit is connectable to the electromagnet to form a closed loop and has impedance means for dissipating stored energy with gate means between the closed loop and the source producing current flow from the source through the closed loop when the residual potential drops to the potential of source and produce reverse current flow through the magnet. The circuit also has a reverse current limiting means in parallel with the impedance means and includes a manually variable resistor to adjust the limit of reverse current flow.