Hisoinc HS125 is a compact personal voice amplification system for people with low-volume speech (very soft speaking voices or esophageal speech). It is useful for people with Parkinson"s, MS and other conditions that cause a strain on the larynx. It is also ideal for professionals who place heavy demands on their voices, including teachers, trainers and trade show presenters.It comes with one lapel and one headset microphones and an AC/DC adaptor for charging the batteries and 6 AA NiMH rechargeable batteries. Specifications: Max Power output: 6 W; Distortion factor: 5% Max (at 2Watt output); Frequency response: 100 Hz --- 10KHz +- 3dB; Operating voltage: 10V-12V.