An electronic circuit and an associated method used to drive an electric motor provide a user selectable relationship between rotational speed of the electric motor and phase advances of signals used to drive the electric motor. The lifting sling comprises an elongated, flexible member having a working surface, a lifting end portion for attaching to a lifting mechanism and a choker end portion. The coupling section is protected from switch gasses emitted from the switch gas outlet opening by means of a shield. The first weighting member is attached to the front of the main body frame, and the second weighting member is attached to the underside of the main body frame.