The term external pilot refers to:

• A. A pilot signal generated internally by the valve
• B. An external source providing the pilot signal
• C. The main hydraulic supply
• D. A mechanical actuator

Answer: (B)

External pilot means the control signal that operates the valve comes from a source outside the valve body. In a pilot-operated hydraulic valve, a small pilot valve uses this external input to pressurize a pilot line that shifts the main valve. This is different from an internal pilot, where the valve generates its control signal from within itself, and from using the main hydraulic supply as the signal, which would just be supplying power rather than a distinct pilot actuation. A mechanical actuator is a separate method of moving the valve, not a hydraulic pilot signal. So, the defining idea is that the pilot signal originates from an external source.