Centerstage WKM-2 Wireless Karaoke Mixer with two wireless handheld microphones plus two inputs for microphone or instrument - Volume, Tone and Echo control - 3.5mm input for smartphones or tablets Accepts up to 4 microphones: Two wireless (included) and two wired. Echo and tone control for all 4 microphones Volume control for both wireless and wired microphones RCA and 3.5mm stereo input This is a single fixed-frequency wireless system. Please consult the manufacturer to confirm compatibility when attempting to use two or more of this system simultaneously or use it with other wireless systems.