Figure 5A shows the symbol used to indicate electrical or solenoid operation. These valves are usually energized by a coil of wire called a solenoid. Figure 5B shows the symbol used to indicate an air operated valve. These valves are activated by pressure pushing on a diaphragm. These valves are commonly called pilot valves.

Sometimes valves can be energized by more than one actuator. In Figure 6, the symbol for an air pilot and a solenoid are stacked on top of each other. In this case it takes an electric solenoid and air pressure to energize the valve. If either one is missing the valve will not energize. In Figure 7, the symbol for manual operation and an electric solenoid are next to each other. In this case the valve can be energized either by the electric solenoid or by some manual means, usually a pushbutton. Being able to activate the valve manually can be very desirable because it can make isolating a problem easier.

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