Final answer:
A sensor detects the position of the piston in a double-acting cylinder and generates an output signal when it passes the sensor at the stacking station.
Step-by-step explanation:
In engineering, a sensor can be used to detect the position of the piston in a double-acting cylinder. When the piston passes the sensor at the stacking station, it generates an output signal. This signal can be used to trigger other actions, such as controlling the movement of a conveyor belt or activating a sorting mechanism.