🔍 Key Concepts

• Servo control in hydraulic systems and what it actually controls (position vs pressure vs flow). • How a variable displacement hydraulic pump changes output when the tilt box or swash plate angle is moved. • What the tilting box control arm at the right side of the illustration is mechanically linked to and why that matters.

💭 Think About

• Look at how the lever on the left moves the internal spool and how that motion is transmitted all the way to the tilting box control arm on the right. What quantity is really being adjusted? • Ask yourself: does this device react to pressure in the line, or is it primarily moving a mechanical element to change pump displacement? • Compare each answer choice with the physical parts you see: which function clearly requires a feedback linkage, a piston, and a control arm like the one shown?.

✅ Before You Answer

• Identify what the tilting box control arm does in a variable displacement pump (what changes when that arm moves). • Decide whether the illustrated device looks more like a pressure‑regulating valve, a flow‑control valve, or a positioning servo for a mechanical element. • Trace the flow paths from ports D and E and confirm whether they are being used to hold a constant pressure, or to move the actuator until a new mechanical position is reached.