Each module requires two or three control pressures to operate
the valves, depending on the valve logic. ZOC16, ZOC17 and all DSA
modules require three pressures. Two of the pressures control the
normal valve modes. The third pressure controls a separate purge
The different modes of operation are obtained by applying the
control pressures in a logical sequence. Truth Tables may be found
in the appropriate module hardware manual that show the logic
required for proper operation.