It provides wireless audio transmission to the Califone® PA919SD, PA919, PA919PS PA systems and can be used for indoor and outdoor applications. We encourage you to visit our website to register your M319 at califone.com/ registratiom for its warranty coverage, and while there sign up for our newsletter and also learn more about the complete line of Califone audio visual products including: Portable and installed wireless PA systems, multi-media players & recorders, headphones and headsets, comp