Analysis of information sources in references of the Wikipedia article "UVB-76" in English language version.
Perhaps the best-known is the Russian UVB-76, a misheard version of its first call sign, UZB-76. Transmitting on 4625 kHz, it was first noticed around the late 1970s, earning the nickname 'the Buzzer' because of its 24-hour droning hum.
For most of its existence, which has been traced back to an original airdate in 1976, it has transmitted a short, high-pitched buzz, every few seconds.