Interlocking devices are generally used in combination with protection devices, and interlocking protection devices can be used alone. Interlocking device is a mechanical, electrical or other device used to prevent dangerous machine functions from running under certain conditions (usually as long as the protection device is not closed). Interlocking devices are generally used with protective devices to achieve the following functions: before the protective device is closed, its "shielded" dangerous machine function cannot be performed; When the dangerous machine function is running, if the protective device is turned on, a stop command will be issued.

Interlocking protection system includes input equipment, logic structure and output system. The input system can be cam, hinge and bolt of mechanical interlocking part, the logic system includes AC contactor and intermediate relay, and the output equipment includes circuit breaker. The process of protection is to obtain the state (on and off) of the protection device through actuators such as cams, and then make logical judgments through electrical signals/optical signals/electromagnetic signals, and finally output them as control signals to control the start or stop state of the equipment. If the protective door is opened and the contact switch of the output system is closed during the normal operation of the equipment, the logic judges that the protective door is opened and the equipment will be automatically powered off. In both cases, it is to prevent the risk of personnel exposure when the equipment is running. Of course, there are many other details of the interlock protection system, including the interlock protection system, the requirements of forced disconnection structure, the selection of interlock devices, the safety design of the interlock protection system, and the reduction of artificial shielding.