Bugs are nearly undetectable monitoring devices. They enable the individual to hear (or to record for later monitoring) conversations. Typically, a bug array is packaged as a small rod containing up to 50 implantable bugs. They are placed by touching the rod to a wall joint, light switch, or some other feature of the room. Implanted bugs are not recoverable, but they can be destroyed.
It does not function in a vacuum: it relies on a gas, a fluid or a solid to carry sound. Bugs send a constant signal to a central monitor (usually disguised as a recreational audio recorder). The range of the bug transmitter is small, usually under 10 meters. The battery for each bug transmitter lasts about five hours with continuous use, longer if it is quiet.
Bugs come in one of four types (based upon the essential principles used for the bug) classified as A, B, C, and D.