Surveillance Laws Governing The Workplace - Pennsylvania

I recently had a customer ask me if there was any documentation available that could be posted and or distributed to there employees which covers the use of video surveillance in the workplace. Here in PA we typically tell our customers to post signage indicating that cameras are in use and recording, keep the audio turn off or at the very least don't record audio, and keep the cameras out of any area where there is a certain expectation of privacy. However, some of the employees still feel having cameras watching over the manufacturing area is illegal. Any suggestion would be appreciated.