Pneumatic wave-generators are known in the art and are typically employed for creating various wave patterns in a water-filled wave-pool.  Such wave-pools have become very popular at water amusement parks and municipal parks in the United States, as well as in foreign countries. 
Known wave-pools generally comprise a caisson structure located at one end of a long swimming pool.  The caisson structure is divided into a plurality of wave-generating chambers.  These chambers are aligned side-by-side across the end of the pool.  Each chamber is sealed except for a below-the-water passageway into the pool, and a valve assembly above the water line to selectively admit pressurized air into the chamber.  Forced air, as from a motor-driven blower, is directed into various of the chambers through the valve assembly, forcing water downwardly into the chambers and through the below-the-water passageway so as create waves in the pool.  After pressurization of a chamber, the air must be vented out to allow water to return to its normal level in the chamber. 
Different wave patterns may be created by forcing air into the chambers in various combinations and sequences.  This is achieved, in part, by controlling the valves into the various chambers. 
Schuster al.  U.S. Pat.  No.  3,629,877 discloses a wave-pool having a plurality of chambers and an air-directing valve arrangement for forcing air into the chambers for creating waves in the pool.  The Schuster air-directing valve arrangement includes a two-way valve device which connects a source of forced air to two adjacent wave-generating chambers in a fixed relationship.  Each chamber has an inlet-outlet passageway for receiving air by way of the valve arrangement and for exhausting air into the surrounding atmosphere, typically in an equipment room.  The Schuster two-way valve arrangement directs air into one of the two adjacent chambers while exhausting air from the other of the adjacent chambers.  This arrangement does not allow the forcing of air into both chambers simultaneously, and thus limits the combinations of wave patterns that may be generated. 
Another pneumatic wave-generator takes the form illustrated in the Bastenhof U.S. Pat.  Nos.  4,467,483 and 4,558,474.  The particular valve device disclosed in the Bastenhof patents includes air inlet and air outlet openings coupled together with a common drive.  Bastenhof permits pressurization of all the wave-generating chambers in any order or pattern, including simultaneous pressurization.  Bastenhof also discloses the use of a common plenum to connect two or more valves to one source of forced air. 
Kreinbuhl et al.  U.S. Pat.  No.  4,730,355, discloses yet another form of wave-generator.  In Kreinbuhl, a four-way air-directional valve assembly connects a source of forced air to associated pairs of inlet-outlet passageways communicating with adjacent wave chambers.  The valve in Kreinbuhl permits four conditions: (a) air can be directed into both adjacent chambers simultaneously; (b) air can be directed into one chamber while the other chamber is exhausted; (c) the opposite of (b); or (d) air can be exhausted from both chambers. 
As can be seen from the above-referenced art, each of these systems have a substantial amount of equipment and moving parts, and there are often large forces on the parts which increase their wear and reduce their life.  Because maintenance and repair is of significant concern to water-park operators, it is important to minimize the number of moving parts employed for creating the various wave patterns, and to reduce wear and tear on those parts which do move thereby improving reliability and simplifying maintenance.  In addition, to reduce operating costs, it is desirable to have a system which efficiently controls and directs air into the wave chambers.