Pneumatic solenoid valves 350241–350245 function as 3- or 4-way pneumatic solenoid valves. They are used to control single- or multi-port pneumatically driven pumps in single-line systems. Timer- and pressure-controlled air is supplied to the pumps for forward strokes. Return strokes are performed by spring force (for 3-way valves) or air force (for 4-way valves). The pumps then force lubricant into the connected metering devices.