Precision and Endurance: The Sine Wave Resonance Generator uses a low temperature drift crystal oscillator and a special chip for high precision DACs to accurately output frequencies and pure sine waves. Premium materials ensure endurance. Stable and Reliable: This Sine Wave Resonance Generator ensures stable frequency output with a default of 7.83 hz. In addition to 7.83 Hz, the following frequencies are also beneficial to your body: 0.83, 6.5, 14.3, 20.8, 27.3 and 33.8 Hz (33.81 Hz). Compact and Portable: The Schumann Wave Adjustable Signal Generator is compact in size and easy to carry around, so you can use it at home or when travelling. How to Use: Take out the included USB cable, plug the round hole end into the circuit board, and the USB end into a power bank or USB charging head or other USB-powered device. Simple to Use: Press the key to input other frequencies by yourself and then press the OK button. Sine signal voltage amplitude of 3V., Manufacturer: shaojian