Where can people learn more about Audio Surveillance equipment? There are several organizations that design and build Audio Surveillance and Audio Monitoring equipment.
To read up on them, you may check out:
http://www.gcomtech.com for Audio Surveillance Equipment including room transmitters, phone transmitters, and surveillance transmitters
http://www.cellularintercept.com for Cellular Interceptor Equipment, a form of Audio Surveillance to monitor mobile phone communication
http://www.secintel.com/c-1-audiosurveillance.aspx for Audio Surveillance equipment to deal with voice and data communication
Where can people learn more about Surveillance?
http://en.wikipedia.org/wiki/Surveillance for an online collection of information on surveillance, techniques, and technologies.
http://web.jjay.cuny.edu/crj/ for information on criminal justice operations and issues that include surveillance training.