An apparatus for operating a gas valve in a gas-fired heating system includes a solenoid having a pick coil and a hold coil connected to the pick coil and to a thermo-generator. The lighting device is fault tolerant due, in part, to the patterning of one or both of the electrodes into strips, and each of one or more of these strips has a fuse formed on it. The medical device sheath is movable relative to the outer sheath and relative to the inner tube. In further embodiments, the piston is rigidly coupled to another, oppositely-orientated second piston, and the two pistons move in unison in response to combustion events to drive hydraulic fluid to a hydraulic motor.