The built-in microphone of a Tentacle needs plugin power on the MIC input for being able to operate. If you like to record it as a reference additionally to the audio timecode you need to set the menu of your camera accordingly. Most of the DSLR and Mirrorless cameras offer this feature but not all of them. If your camera does not support plugin power but you still would like an audio reference signal to be recorded you would have to use an external microphone that is powered by batteries and connect it with the help of a y-splitter cable.