I had this type of issue come up lately as well. A municipal customer had the cities IT dept install a wireless music system through out the downtown area. They also decided that it would be nice if they could input the audio during the concerts they put on so that it can be broadcast throughout the area. So, I so up for a show and they inform me their great idea. They show me the transmitter (with out and information or manual). I see an XLR input, no problem. I plug in a send from the board, no sound. An hour and a half of troubleshooting later, I figure out that the input in unbalanced stereo on an xlr.