First comment from this forum :
"The environment is a classroom. I purchased a Shure wireless receiver with a PGX4 body pack and lavalier mic which works great but only picks up audio from the teacher but not the students. I contacted Tandberg to ask about the Audio science ceiling mount microphone but the sales person laughed as he rattled off the price and told me to just buy a regular microphone and put it at the front of the class. I think I need a mixer in order to continue to hear the teacher's mic, and I know I want minimal wiring on the ground to avoid any accidents. I would really appreciate some tips on how best to approach this.
Thanks!"
see this forum at : http://www.vtctalk.com/showthread.php?t=25186