The Model EJ-2Plus is a compact multi-input adapter compact & lightweight that accepts line level output from either a laptop computer, audio cassette player, CD player, DVD player, or video tape player for insertion into a P.A. system. It is designed to provide the user with an easy to use, easy to carry, high quality interface for the audio content of a presentation, while providing the necessary matching and isolation for the existing PA system. no batteries or external power required The EJ-2Plus is a passive device, so no batteries or external power sources are required for operation. The EJ-2Plus includes cables with a 3.5mm stereo plug and a pair of RCA plugs for making connection to your audio content for laptop or other audio/video device, and a standard 3-pin presentations made easy XLR for connection to the microphone input of an existing sound system. It also comes with a nylon carrying case. An instruction card comes stored in a pocket of the carrying case. The EJ-2Plus does have its’ own volume control. It also audio interface for comes with a hum switch, which allows you to disconnect laptop computers the circuit from ground if you encounter a humming or feedback problem when you connect to an existing P.A. system.