In a four-port, two-position valve, which port is typically used as the exhaust or tank return?

• A. Pressure (P)
• B. Tank/Exhaust (T)
• C. A (Port A)
• D. B (Port B)

Answer: (B)

In a four-port, two-position valve, you have a supply port (P), two working ports that connect to the actuator (A and B), and an exhaust path (T). The exhaust or tank return is the port labeled Tank/Exhaust because it is the outlet through which air leaves the system after it has pushed the cylinder or when that side of the circuit is vented. In one valve position, pressurized air from P goes to one working port (say A) while the other working port (B) dumps to exhaust (T); in the other position, P connects to the other working port (B) and A dumps to exhaust (T). This setup lets the actuator be driven in both directions and then vent the spent air through the exhaust path. The other ports serve different roles: P is the supply, and A and B are the two sides of the actuator, not the exhaust themselves.