Limit Switches are a type of control switch that is actuated by the movement of machine parts or operator action. They are commonly used in various industries to control the position, speed, or sequence of operations in mechanical and electrical systems.

Definition:
A limit switch is an electrical switch that is mechanically operated to open or close a circuit. It is typically used to control or signal the position of a machine component or to provide feedback on the status of a system.

Function:
Limit switches serve several functions, including:
1. Position Control: They can be used to stop a machine at a specific position, ensuring that parts are aligned correctly for assembly or processing.
2. Safety Interlocking: They can be used to prevent access to dangerous areas of machinery when it is in operation.
3. Sequence Control: They can be used to control the order of operations in a process, ensuring that steps are completed in the correct sequence.
4. Overtravel Protection: They can prevent a mechanism from moving beyond its intended range of motion, which could cause damage or injury.

Applications:
Limit switches are used in a wide range of applications, such as:
1. Industrial Machinery: They are used in conveyor systems, packaging machines, and robotic arms to control movement and positioning.
2. Automated Systems: In automated production lines, limit switches ensure that parts are in the correct place before a process begins.
3. Elevators: They are used to control the movement of elevator cars and to signal when they have reached a floor.
4. Garage Doors: They are used to stop the door from closing when an obstruction is detected.
5. Medical Equipment: In medical devices, they can control the movement of parts or signal the completion of a procedure.

Selection Criteria:
When selecting a limit switch, consider the following criteria:
1. Environment: The switch should be rated for the environmental conditions it will be exposed to, such as dust, moisture, or temperature extremes.
2. Mechanical Load: The switch should be able to handle the force exerted by the machine part that will actuate it.
3. Electrical Rating: The switch should have the appropriate voltage and current ratings for the circuit it will be used in.
4. Actuator Style: The switch should have an actuator that is compatible with the mechanism that will it, such as a lever, roller, or paddle.
5. Mounting Options: The switch should have mounting options that allow it to be securely and conveniently installed in the desired location.
6. Response Time: The switch should have a fast enough response time to prevent any delay in the control system.
7. Durability: The switch should be designed for long life and reliability, especially in applications where it will be actuated frequently.

In summary, limit switches are essential components in many mechanical and electrical systems, providing critical control and safety functions. Their selection should be based on the specific requirements of the application, including environmental conditions, mechanical loads, and electrical specifications.
Please refer to the product rule book for details.