Photolithographic apparatus, systems, and methods that make use of sub-resolution assist devices are disclosed. The vacuum release mechanism is disposed adjacent the cam and engages a cam follower at engine starting speeds to unseat an engine valve while an engine piston is moving toward a crankcase and away from the combustion chamber. Then, the calling user element transmits the caller image information to the called user element over the data path. A reference signal supplied to each mixer in the receiving mixer is generated based on an FM continuous wave output from an FM modulator.