Radioshack 4-channel Mixer with USB and Sound Effects Incorporate sound effects and combine up to 4 audio sources, including a USB source,Choose from 6 digital sound effects: Laser, Machine Gun, Tron, Siren, Emergency and UFO Easily integrates with amplifiers, speaker and microphones to simplify setup Rack-mountable so you can easily slide it into your sound system with the rest of your equipment Features Echo with variable delay, repeat and level controls, Dual microphone inputs with Talkover so you can announce the next songBlue illuminated channel and master volume controls so you can use it in low-light conditions, Individual rotary controls for Mic 1, Mic 2, bass and treble so you have full control of your sound,Assignable A/B cross-fader and user-replaceable cross-fader