The A-Source Diamond Tester utilizes proven thermal conductivity testing method to instantly verify the authenticity of diamonds. A positive diamond test is indicated with an audible beep and a green light. Operates on three alkaline (AAA) batteries or direct AC current. Features: A Highly sensitive and heavy duty tip design, Color LED display (Green & Red), Pocket Size Factory calibrated, no adjustment necessary, Auto power shut down after 10 minutes of non-use, Sleep-mode beep, Low Battery Indicator, Visual and audio indication of Diamond, Soft Carrying case, 2 year factory warranty Note: The A-Source Diamond tester, like any thermal conductivity tester, cannot eliminate Synthetic Moissanite.