The product is composed of an electromagnet, an armature, a friend of mine, liner and base composition, product size about 100 x 70 x 125mm, instrument working voltage: DC3 ~ 6V. DC resistance of solenoid coil is 10 ~ 20; adopting 55mm domestic iron bell bicycle bell cap; lining board, the base is made of plastic. Product sound effects: within 15 meters, the bell rings clearly.