"UVB-76, also known as The Buzzer, is the nickname given by radio listeners to a shortwave radio station that broadcasts on the frequency 4625 kHz. It broadcasts a short, monotonous buzz tone, repeating at a rate of approximately 25 tones per minute, for 24 hours per day. On very rare occasions, the buzzer signal is interrupted and a voice transmission in Russian takes place. It has been active since sometime in the late 1970s or early 1980s, when the first reports were made of a station on this frequency. Its origins have been traced to Russia, and although several theories with varying degrees of plausibility exist, its actual purpose has never been officially confirmed and remains a source of speculation."
"Frequently, distant conversations and other background noises have been heard behind the buzzer, suggesting that the buzzing tones are not generated internally, but are transmitted from a device placed behind a live and constantly open microphone."
"There are two other Russian stations that follow a similar format, nicknamed "The Pip" and "The Squeaky Wheel". Like the Buzzer, these stations transmit a signature sound that is repeated constantly, but is occasionally interrupted to relay coded voice messages."
