I was a CB radio enthusiast in the early 70s, the readability (comprehension of the spoken word) scale of the audio on CB was Zero (0) to Five (5).
the signal strength was on a scale of Zero (0) to Nine (9) so if you were a long distance away with a weak signa but your spoken words were clear the response could be reading you 3 (signal strength) by 5 (comprehension).