I should clarify that by “intelligible” I meant that a human can make out the symbols being said (words or numbers) and write them down for later decryption, no

I should clarify that by “intelligible” I meant that a human can make out the symbols being said (words or numbers) and write them down for later decryption, not that their meaning is readily obvious to people without special knowledge. It sounds like UVB-76's broadcasts (when it's not just buzzing) would be “intelligible” in the sense I was thinking. The Japanese Slot Machine seems like something only machines could work with.