UVB-76 Activity Picking Up Over Last Several Days
August 26th, 2010

Via: Wikipedia:

UVB-76 is the callsign 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. Only four to five such events have been noted. Despite much speculation, the actual purpose of this station remains unknown to the public, but it is probably used for relaying military orders. There has been a spike in activity as of late August, 2010.