OBTW is correct, it's a VOX circuit and the coversation will be very choppy in a high background noise environment.
I have installed a few and IMHO, they work great in an area used for office/storage, but not for any manufacturering or forklift traffic. The other problem is the employees that have a shop radio playing in their area.
I hope you are aware that you must have a spare CO port on the phone system to use this type of paging as well.
