The Buzzer testing multiple transmitters
Here is almost a hour of Russians testing multiple separate transmitter sites The Buzzer has - but every one of them at the same time, and at varying frequencies! This kind of occurrence is totally new and pretty interesting. Playing some test tones, some feedback audio noise and even MS-5 (CIS-12) data transmission!
This could be some maintenance or renovation of the audio feed to all of the transmitter sites at the same time. Transmitter sites are in separate areas of west Russia.
More info:
https://priyom.org/military-stations/...
https://www.sigidwiki.com/wiki/CIS-12