A bistable electronically controlled pneumatically powered transducer for use, for example, as a valve mechanism actuator in an internal combustion engine is disclosed. The transducer has a piston which is coupled to an engine valve, for example. The pistion is powered by a pneumatic source and is held in each of its extreme positions by pneumatic pressure under the control of control valves which are in turn held in their closed positions by pressurized air and/or permanent magnet latching arrangements and are released therefrom to supply air to the piston to be pneumatically driven to the other extreme position by an electromagnetic neutralization of the permanent magnet field. A pair of auxiliary pistons movable with the piston compress air to a pressure above the pressure of the pneumatic source for aiding reclosure of the control valves as well as aiding maintenance of those control valves in their closed positions thereby reducing the size and cost of the latching permanent magnets. Air return springs for the control valves are formed by annular chambers which are sealed by initial control valve motion away from their respective closed positions. Thereafter, the chamber size diminishes linearly, and the chamber pressure increases approximately linearly, with further control valve motion thereby providing a restorative force to the control valve which increases as the valve opens.