What does a readability of 1 indicate about a transmission?

A readability of 1 in the context of radio communications specifically indicates that the transmission is unreadable. The readability scale typically ranges from 1 to 5, where 1 signifies that the message is impossible to understand due to poor conditions or severe interference, while a higher number would indicate an increasing level of clarity.

Therefore, a readability of 1 does not imply that the transmission is unclear in a general sense but rather that it is beyond comprehension, signaling a communication failure rather than just a degradation in quality. It is essential for pilots and air traffic control to understand this scale to make proper assessments of communication effectiveness during operations.