The ECM-AW4 Bluetooth Wireless Microphone System from Sony 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 150 feet.This mic system allows a subject and a device operator to communicate, eliminating the need for a separate intercom system. In this way the camera operator can act as a director, giving direction or suggesting interview questions to the onscreen talent, even if they are out of ear shot. A 3.5mm headphone jack/audio output is provided on both the transmitter and the receiver to facilitate this feature.For mounting or wearing the microphone and receiver, a belt clip and an arm band are included. The arm band enables you to attach the transmitter to a subject that is wearing clothing that cannot accommodate a belt clip. An included carrying pouch will help to protect the transmitter.