individually connect with corresponding pneumatically operated selector valves typified by valve 64 which transmits a modulated pressure signal through the pressure regulator 65 to the air cylinder unit 41 for proper adjustment of the valve assembly 32 with respect to valve orifice plates 18 and 22 line 66 bypasses the pressure regulator for the purpose of permitting escape of air from the cylinder 41 through the four way selector valve 64 during settings of the valve mechanism requiring reduction of pressure in the unit 41 air lines 67 and 68 are merely of lines leading to other apparatus similar to that connected with line 69 for serving each nozzle and valve assembly fig6 illustrates a modified air dispenser 70 comprising walls defining hot and cold air chambers 71 and 72 and a manifold 73 having a nozzle 74 the manifold defines a valve chamber at 76 within which a partly cylindrical valve element 77 is rotatable in opposite angular directions about its fulcrum shaft 78 to increase or decrease the air passing from the hot branch 81 of the manifold into the nozzle 74 while correspondingly decreasing or increasing respectively the air passing from the cold branch 82 of the manifold to the nozzle automatic operation in proportioning the air passing from the passageways 81 82 is effected through a lever 83 connected by linkage 84 to the reciprocatable push rod 85 of an air cylinder 80 which may be similar to air cylinders 41 of the previously described embodiment automatic control of the hot and cold air mixture entering the nozzle 74 may be effected by the apparatus of fig8 as hereinbefore described with.