Hidden electronics detection

A brief history of electronic eavesdropping (bugging) is given, and techniques used by persons wishing to gain confidential information are described. Various methods of detecting radiofrequency transmitting devices are explained as are the limitations of conventional means for locating them. A device capable of transmitting an extremely pure fundamental signal at 915 MHz and listening to a harmonic signal reflected by semiconductor devices is explained. Its theory of operation and its component circuits are described.<>