Readability

R1 Unreadable.
R2 Barely readable, occasional words distinguishable.
R3 Readable with considerable difficulty.
R4 Readable with practically no difficulty.
R5 Perfectly readable.
 

Signal strength
 

S1 Faint, signals barely readable
S2 Very weak signals
S3 Weak signals
S4 Fair signals
S5 Fairly good signals
S6 Good signals
S7 Moderately strong signals
S8 Strong signals
S9 Extremely strong signals
 

Tone
 

Tl Extremely rough hissing note
T2 Very rough ac note, not musical
T3 Rough, low-pitched ac note, mod. music
T4 Rather rough ac note, mod. musical
T5 Musically modulated note
T6 Modulated note, slight trace of whistle
T7 Near dc note, smooth ripple
T8 Good dc note, just a trace of ripple
T9 Purest dc note