Hornet “do … do-do” sound warning

[MivwTaupos]

what is the “do .. do-do” sound keep warning mean after setting CRS at 14:30 in the video? Thank you 
 

 

[Hulkbust44]

That's the morse code identifier for the tuned TACAN station.

Sent from my moto g stylus 5G (2022) using Tapatalk