Number stations time signals & other strange transmissions are not only interesting but they provide a good benchmark for propagation.
RWM is a Russian shortwave time signal station. The station transmits in Morse from Moscow on 4996 kHz, 9996 kHz and 14996 kHz.
Take a listen on 4624kHz in the evenings and you’ll hear the Buzzer.
Here is an article on the Buzzer by the BBC