The Cold War Bug That Needed No Battery

Hidden inside a wooden gift given to a US diplomat, a Soviet listening device worked for seven years without any internal power source. It relied entirely on an external radio beam to activate.

The device was a simple resonant cavity that only broadcasted sound when hit by a specific radio signal from an outside transmitter. Because it lacked batteries or wires, it was nearly impossible for security experts to detect for years. This clever piece of espionage essentially functioned like a primitive RFID tag. Today, the design is studied as one of the earliest ancestors of modern contactless technology.