The station’s callsign is “UVB-76”, but is known amongst enthusiasts as “The Buzzer”, and the sound it transmits has been on an almost continuous loop since it was first observed in 1982.

No one knows for sure what the purpose of the signal is, and in 27 years the buzzing has only been interrupted on 3 occasions.

At 21:58 GMT on Christmas Eve 1997, 15 years after it was first observed, the buzzing abruptly stopped; to be replaced by a short series of beeps, followed by a male voice speaking Russian who repeated the following message several times:

“Ya — UVB-76. 18008. BROMAL: Boris, Roman, Olga, Mikhail, Anna, Larisa. 742, 799, 14”.

On September 12th 2002 another voice was heard, this time so distorted that only part of the message could be recognised:

“UVB-76, UVB-76. 62691 Izafet 3693 8270”.

Finally, on February 21st 2006, a third message2 was transmitted which said:

“75-59-75-59. 39-52-53-58. 5-5-2-5. Konstantin-1-9-0-9-0-8-9-8-Tatiana-Oksana-Anna-Elena-Pavel-Schuka. Konstantin 8-4. 9-7-5-5-9-Tatiana. Anna Larisa Uliyana-9-4-1-4-3-4-8.”

The names used in the message are used in some Russian spelling alphabets, and although some people speculate that UVB-76 is a specialised Numbers Station, used to transmit encoded messages to spies, the messages have never been decoded, and the actual purpose of this station remains unknown.

There’s more information about the mysterious UVB-76 at WIkipedia. Thanks to Best of Wikipedia.