The Sony ECM-AW4 Bluetooth Wireless Microphone System is a complete battery-powered Bluetooth wireless microphone system. It plugs into virtually any kind of video camera, DSLR, or recording device that features a 3.5mm mini-jack microphone input. The transmitter has a built-in mic, or you can use a separately available external mic with 3.5mm output (Plugin Power supported). Receiver unit has a talk-back function that allows the camera operator to communicate clearly with the subject. The mic has a range of up to 45 metres. Wide Compatibility Compatible with nearly any video camera or portable audio recorder with a 3.5mm mini-jack microphone input Two Way Communication From up to 150 feet line-of-sight away from the camcorder, you can shoot while recording whole conversations with each other One Way Communication Select to pick-up only the voice of the subject, or both the subject's and the camera operator's voices Separate Earphones Two separate earphones are provided for both the microphone and the receiver units Up to Three Hour Battery Life Operates for up to three hours when running continuouslyIn standby the microphone battery lasts up to nine hour and the receiver battery up to three hours