This product is Schumann wave 7.83HZ very low frequency generator, features high accuracy and stability. High stable frequency acquisition elements: high stability chip, correction capacitance, multi-loop adjustable resistor. High quality polymer batteries, with overcharged, overvoltage, overcurrent protection. There is almost no voltage ripple in the voltage supply. With work toggle switch, easy to . Schumann wave can be applied to HIFI or . : 12V 1A android charging cable Polymer battery capacity: 2300mah Working time: 200 days(full of ) Material: Metal colour: black Package Contents: 1 x Ultra-low frequency generator Only the above package content, other products are not included. Note: Light reflection and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.