Ultra-Low Frequency Pulse Generator Sleep Improver 7.8Hz Schumann Waves USB Pow Features: Schumann resonance (SR) are a set of spectrum peaks in the extremely low frequency (ELF) part of the earth's electronmagnetic field specturm. This schumann waves generator with high precise and fine stability, give you a better using experience. You need to connect it with the power by type-c cable, no battery included, which is convenient to use. You can use it in your home to reduce your insomnia, also can use it in the office to improve work efficiency. It has a wide ranges of uses. Easy to operate, you can use it directly after plug in the power, whether you are a novice or an amateur, you can use it quickly. Specifications: Material: plastics Disk diameter: 82mm / 3.2in Power supplys: Type-c port Resonant frequency: 7.8Hz (adjustable) Package size: 100 * 82 * 20mm / 3.9 * 3.2 * 0.8in Package weight: 18g / 0.6ounce Packing list: 1 * Schumann Resonance Generator