RST reporting system

When listening to amateur radio Morse code transmissions you will often hear the phrase:

UR RST 599 OM.

This is a reference to the RST signal reporting system. The three letters refer to Readability, Signal strength and Tone. Here is a summary of the meaning of the numbers:

Readability:

1 Unreadable signal to 5, Perfectly readable

Signal strength:

1 Very faint, just about detectable to 9, extremely strong signal

Tone

1 Very noisy, bad signal to 9, perfect tone

So, RST 588 means:

“Your signal is perfectly readable and fairly strong with almost perfect tone.”