The expansion mic is wired and plugs in to the back of the camera. The expansion microphone does not have Bluetooth capability but does have a Bluetooth indicator light which flashes when you have a Bluetooth device connected to the camera. You can connect a Bluetooth device such as a phone to the camera to push the audio to the camera (eg when on a call).
The expansion microphone connects to the back of the webcam itself
This product is designed for use in small conference rooms. The optional expansion microphone will boost the range and allow use in larger rooms