During his work at the sharashka, where he was put in charge of other workers, Theremin created the Buran eavesdropping system. A precursor to the modern laser microphone, it worked by using a low-power infrared beam from a distance to detect the sound vibrations in the glass windows.[4][29] Lavrentiy Beria, the head of the secret police organization NKVD (the predecessor of the KGB), used the Buran device to spy on the British, French and US embassies in Moscow.[29] According to Galeyev, Beria also spied on Stalin; Theremin kept some of the tapes in his flat. In 1947, Theremin was awarded the Stalin prize for inventing this advance in Soviet espionage technology.