The R-S-T System

Readability

1 - Unreadable
2 - Barely readable, occasional words distinguishable.
3 - Readable with considerable difficulty.
4 - Readable with practically no difficulty.
5 - Perfectly readable.

Signal Strength

1 - Faint signals, barely perceptible.
2 - Very weak signals.
3 - Weak signals.
4 - Fair signals.
5 - Fairly good signals.
6 - Good signals.
7 - Moderately strong signals.
8 - Strong signals.
9 - Extremely strong signals.

Tone

1 - Sixty-cycle ac or less, very rough and broad.
2 - Very rough ac, very harsh and broad.
3 - Rough ac tone, rectified but not filtered.
4 - Rough note, some trace of filtering.
5 - Filtered rectified ac but strongly ripple-modulated.
6 - Filtered tone, definite trace of ripple modulation.
7 - Near pure tone, trace of ripple modulation.
8 - Near perfect tone, slight trace of modulation.
9 - Perfect tone, no trace of ripple or modulation of any kind.

If the signal has the characteristic steadiness of crystal
control, add the letter x to the RST report.  If there is a
chirp, the letter c may be added to so indicate.  Similarly
for a click, add k.  This reporting system is used on both
CW and voice, except that the "tone" report is left out on
voice.