... 4ghz,mic built in 5.wireless microphone Wireless Microphone for Teachers,USB Wireless Microphone,Bluetooth Wireless MicrophoneFor handsfree convenience, ... 4GHz emitter, microphone and processor are combined in this all-in-one unit, for revolutionary, cable-free convenience. ... Feature:1.Portable,convinient,microphone hands free,USB jack2.Certificate: ...