Two gears can not be used at the same time or it will get burned Charging: 3 holes are charged separately. Each hole is charged for about 30 minutes one by one. When all three holes are charged, the whole battery is fully charged. When the indicator light of the charger, green light, is off, it means that it is fully charged Pay attention to the use time: do not use it for more than 10 seconds each time. Use it for 3 times continuously. Take 20-30 seconds to cool down the instrument. Prevent it from burning out due to high temperature Principle: The EMP Generator produces a high-frequency electromagnetic wave field. An energy-saving lamp around the generator induces electromagnetic waves and generates an electric current. When the electric energy is sufficient, the bulb will light up. PS: There is no guarantee that the energy-saving lamp will work. If it is on, it proves that the meter is working. Specfifications: Frequency: 150MHZ Typical applications: Fingerprint lock, slot machines, claw cranes, game machines, etc. Working voltage: DC 36V Antenna mode: built-in reinforced antenna + external high-frequency antenna Power supply voltage: DC 36V Charging time: 1.5 hours in total Charger: input110-220 VAC Built-in rechargeable battery Plug Type: US Plug, it applies to Canada, India, Mexico, Thailand, Taiwan, the United States, the Philippines and so on. Colour:White Material:plastic Voltage: AC100-240V Package Contents: 1 x EMP Generator 1 x Power Adapter 1 set x accessories Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.