*This product is used for middle school physics teaching to understand and study the basic structure and working principle of electromagnetic relay. *This product can be used with other instruments to perform demonstration experiments such as automatic control and remote control. *This product is mainly composed of electromagnetic system and system. The electromagnetic system includes: electromagnetic coil and iron core armature; the system includes: a pair of normally open and normally closed contacts. *When the coil is energized, the iron core generates magnetism, sucks down the armature, disconnects the power supply of the coil, the iron core loses magnetism, and the armature resets, thereby controlling the controlled circuit. *We attach great importance to customer experience, so you can us if you have any questions, and we will get back to you within 24 hours!