Auditory Conductivity Indicators are a practical alternative to light sensitive LED conductivity indicators. They also provide semi-quantitative information about the materials being tested. When both probes are in contact with a solid, or immersed in a solution, and the material is a conductor, the audible tone increases in volume and intensity as conductivity increases. There will not be any tone if the material is a non-conductor. The indicator comes with a one year limited warranty. (A 9-volt battery is required, but not included). The kit includes a 12 well Chemplate for testing multiple items conveniently. The plate also has a large well built-in for easy rinsing.