Limit switches are used to control the travel and limit protection of mechanical equipment. In actual production, the travel limit switch is installed in a pre-arranged position. When the module installed on the moving parts of the production machinery hits the travel switch, the contacts of the travel limit switch act to realize the switching of the circuit. Therefore, the limit switch is an electrical appliance that switches the circuit according to the travel position of the moving part, and its working principle is similar to that of a button. Limit switches are widely used in various machine tools and hoisting machinery to control their travel and perform terminal limit protection. In the control circuit of the elevator, the travel limit switch is also used to control the speed of opening and closing the car door, the limit of automatic door opening and closing, and the upper and lower limit protection of the car.