Freq: 4625 KHz USB
The UVB-76 (also known by other call signs such as ZhUOZ or MDZhB) is a Numbers
Station based in Russia. It got it's nickname Russian Buzzer from the
buzzer sounding channel marker that is transmitted. Every so often someone
would transmit a series of numbers and words.
It is said that the UVB-76 is a remnent of the Cold War Era, and was used to relay secret messages to spies. There are many theories as to what the station actually was (or even is) being used for. As of 2017, the station is still in operation. At one point, it had went offline a few years ago and apparently had been relocated. Then it came back online and continues operation to this day.
Here is more information on the infamous UVB-76: