We want to use a wired lavelier microphone to record a lecturer in a classroom. The microphone will plug in to a camera that is installed somewhere on the ceiling or wall. What microphone would you recommend? And how far is it possible to extend a microphone? The distance will be about 20 meters. Is it possible to get an extension cable or does there have to be some kind of powered terminal in between to transmit the signal. I know that with USB there is a limit to how long the cables can be. Any suggestions are greatly appreciated.