How does a limit switch operate?

A limit switch operates by detecting physical contact, which is essential in various automation applications. When an object comes into contact with the switch, it activates the mechanism that triggers a specific function, typically related to controlling an actuator. This could involve stopping, starting, or reversing the direction of a motor, thereby allowing for precise control within a given range of motion.

In industrial contexts, limit switches are often used to denote the position of moving parts. For instance, in a conveyor system, when an item reaches the end, the limit switch gets activated, signaling the system to halt or change direction. This functionality is crucial for safety and efficiency in automated processes, ensuring that machinery does not operate out of its intended limits.

Other options fall into categories unrelated to the primary function of seeking contact-based activation. While picking and placing items, sorting, and stacking are all automation tasks, they do not capture the fundamental operation of a limit switch, which is centered around the detection of contact to control actuators effectively. Thus, B highlights the core operational principle of a limit switch, making it the correct answer.