Also known as a "contact mic". When entry is not possible and you need to hear what is being said as well where people are located, this system is essential! Hearing what is happening on the other side of a wall, the floor above, or the floor below your location can provide the intelligence you need to safely conclude the incident. The SAKTM non-invasive audio recovery kit has everything you require to quickly deploy a through-the-wall listening system. The entire system is tuned perfectly for maximum voice intelligibility and stereo imaging.