A system and methods are provided for mixing input signal data values with values of a sinusoidal waveform. Fluid flow through a pilot passage, linking the control chamber and the outlet port, moves an exhaust spool between first and second positions to control fluid flow through passages in the main poppet. The body includes an upper portion, an intermediate portion, and a lower portion, with the upper and intermediate portions, in combination, extending at least 60% of the body length from the second end, with at least the upper and intermediate portions of the body having a width dimension to depth dimension ratio of at least 1. The second pipe wall serves as a low-temperature source. The invention relates to a photoreceptor for electrophotography which has a photosensitive layer containing an aromatic hydroxycarboxylic acid metal complex represented by the following general formula :and one or more charge-transporting agents each having an arylaminophenyl group in the molecule.