A method and apparatus for using a sheet of paper to control document processing is described. Before each clock state change, the clock driver briefly shorts-together the first and second clock signals, to equalize change on capacitive loads, which each assume a potential midway between high and low power supply levels. The gases are cooled between successive stages so as to remove water vapour, and the pressure is reduced before they are subjected to the second stage. The support frame includes a large support axis and a small support axis that cross.