【Electronic Bolt Lock】There are 2 elements, the \"fixed\" part painted in black and the metal hook. You have to slam the door shut to close it and apply 12V to the wires to unlock. The electromagnetic lock is mainly made of carbon steel, the lock hook can withstand a pulling force of 150 kg. 【Connection Precautions】The lock should not be powered for more than 3 seconds and the voltage must be 12V 2A. If you use a relay with a digital code and when you unlock, everything turns off. Since the power supply is not powerful enough, you need to power the coil separately or put a dedicated power supply for the lock. 【Open via Intercom】The lock can be opened via intercom with a little DIY. Just need to send a 12V and 2 amp pulse, so provide a small relay in case of power shortage with a 12V 3 amp power supply. Perfect for securing cabinets, so children cannot access. 【Energy Saving and Long Lifespan】Shockproof, puncture-proof and anti-theft. Mechanical life, when designing the load condition, about 500,000 times. Suitable for a door of 0.5 to 4 kg. 【Easy to Use】Electromagnetic magnetic lock for easy installation, without restrictions on left, right, front, back and which allows the mechanical unlocking position of the flaps. Built-in detection of unlock status. Size approx. 5.7 x 7.2 x 1.3 cm. Use for delivery cabinets, refrigerators, mailbox or newspaper box, self-service cabinets, counter.