1、The user needs to configure an external audio system, K8 microphone supports multiple input connectors including USB audio input/HD Multimedia Interface input/optical input/5mm audio. 2、The volume of the microphone and background song can be adjusted individually through the knob on the back. 3、A professional wireless microphone system with 2 microphones,enjoy music with your friends provide a quality customer experience. 4、With long transmission range approx 66in in open space, ensuring that can simultaneously without worrying about interferences. 5、The microphone system is easy to use with multiple systems and is the perfect microphone system for any professional or entertainment activities. 1 x K8 Home Wireless Karaoke Box2 x Wireless Microphone (not Including 1.5V AA x 2 Battery)1 x DC USB Cable1 x Power Adapter1 x 3.5 MM Audio Cable1 x 3.5MM to 2RCA Jack Audio Cable1 x Manual Item Type: Karaoke BoxMaterial: Plastic + MetalMicrophone Batteries: 2 x AA Batteries Per Microphone (Not Included)Voltage: 100-240VFrequency: 750MHz-769MHzEffective Distance: > Approx. 65.6inFrequency Response: 50Hz-17KHzSignal To Noise Ratio: > 100dBDistortion: < 0.5%