UZB76 (sometimes referred to as UVB76, but recently MDZhB) is the call sign of a shortwave radio station that usually broadcasts on the frequency 4625 kHz (AM suppressed lower sideband).
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.
Despite much speculation, the actual purpose of this station remains unknown to the public.