The position switch is also called limit switch and position limit switch, the function of which is the same as the push button switch, it is only a electric device giving instruction of connecting or disconnecting the circuit or converting the signal to the control circuit etc.. The difference is that the action of the contacts are not accomplished by fingers, but it is a kind of electric device that uses the collision of some moving parts of the production machinery to make the contacts act, connect or disconnect some control circuit in order to reached a certain control requirements. In order to adapt to collision under all kinds of conditions, the position switch has a lot of structure forms, which are used to limit the position or travel of the mechanical movement and to make the mechanical movement automatically stop, reverse or circulated in variable speed in a certain travel, in order to realize automatic control, etc..

The commonly used position switches are LX - 19 series and JLXKI series. The basic structure of various series of position switches is the same in the basic structure, it is composed of contact system and shell. The difference only lies in the transmission device that makes the position switch act. 

The position switches have been widely used in various types of machine tools and lifting machinery, in order to control its position and protect the end limit. In the control circuit of elevator, the limit switch is used to control the speed of the car door and the limit of the door automatically opening and to protect the upper and lower limit of the car door. Generally there are many kinds of limit switches including rotary type and push- button type etc. (shj)