UVB-76 is the callsign of a shortwave radio station that usually broadcasts on the frequency 4625 kHz. It is known among radio listeners by the nickname The Buzzer. It features a short, monotonous buzz tone, repeating at a rate of approximately 25 tones per minute, for 24 hours per day. The station has been observed since around 1982. On rare occasions, the buzzer signal is interrupted and a voice transmission in Russian takes place. Only four to five such events have been noted. Despite much speculation, the actual purpose of this station remains unknown to the public. There has been a spike in activity as of late August, 2010.
Its purpose is unconfirmed. One website claims the station is meant to “Transmit orders to the military units and recruitment centers of the Moscow military district.” However the station transmitted the simple buzz tone for at least 15 years before any words or numbers were broadcast. Because of the nature of the broadcast and the fact that its transmitter location is rumored to be a communications hub of the General Staff of the army, UVB-76 is widely believed to be used to transmit encoded messages to spies, as is generally assumed for the many numbers stations that populate shortwave frequencies.