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. Sometimes, the buzzer signal is interrupted and a voice transmission in Russian takes place. It has been active since at least 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, but although several theories with varying degrees of plausibility exist, its actual purpose remains unknown to the public.