How can you realize an OR logic function with two pressure sources?

How can you realize an OR logic function with two pressure sources?

• A. Wire the pilot signals in series
• B. Use a cascade/sequence logic
• C. Use a shuttle valve to select higher pressure source to feed the actuator
• D. Use a single pressure source

Answer: (C)

In pneumatics, an OR function means the output is energized if either input is pressurized. A shuttle valve realizes this by having two input ports and one output port; the internal shuttle moves to the side with higher pressure, automatically selecting that source and blocking the other. This ensures the actuator receives pressurized air as long as either source is active, which matches OR behavior: output on if any input is on. If both sources are present, the higher pressure source wins, but the actuator still gets pressure through the valve. The other approaches either require both signals to be present, implement different logic structures, or don’t combine two sources at all.

In pneumatics, an OR function means the output is energized if either input is pressurized. A shuttle valve realizes this by having two input ports and one output port; the internal shuttle moves to the side with higher pressure, automatically selecting that source and blocking the other. This ensures the actuator receives pressurized air as long as either source is active, which matches OR behavior: output on if any input is on. If both sources are present, the higher pressure source wins, but the actuator still gets pressure through the valve. The other approaches either require both signals to be present, implement different logic structures, or don’t combine two sources at all.