The history of audio recording itself is intimately tied to the history of espionage. At the KGB Espionage Museum, you can see many of the most famous secret recording devices and hear the stories for how they were used.
The KGB and GRU (Main Intelligence Directorate, or Glavnoye razvedyvatel’noye upravleniye in Russian) spies used recording devices for covert operations in law enforcement, internal security, and espionage. KGB recording devices were irreplaceable objects that KGB agents used to capture information, covertly record conversations, tap telephone lines, bug rooms, and collect incriminating evidence from suspects or enemies.
During the Cold War, the Mi-51 was the world’s smallest recording device. A marvel of technology, it measured only 17 x 11 x 3.5 cm, and was small enough to fit in a pocket or a handbag. It ran on batteries and used a wire to record over two hours of sound. This device was even used by the United States.
Wire recording devices such as the Minifon Mi-55 became the standard for spies, since they were the most durable and trustworthy. They evolved to record more than eight hours of tape, and the technology is still used in flight recorders. These days, recording devices have evolved to be even smaller and more effective and are even usable underwater.