RST code
The RST code is used to describe the readability, strength and tone of a signal. The code consists of three digits, the first one represents the readability, the second one represents the strength and the last one the tone.
Table
| number | readability (R) | strength (S) | tone (T) |
|---|---|---|---|
| 1 | Unreadable | Faint sginal, barely percentible | Sixty cycle a.c. or less, very rough and broad |
| 2 | Barely readable | Very weak | Very rough a.c., very harsh and broad |
| 3 | Readable with considerable difficulty | Weak | Rough a.c. tone, rectified but not filtered |
| 4 | Readable with practically no difficulty | Fair | Rough note, some trace of filtering frequency |
| 5 | Perfectly readable | Fairly good | Filtered rectified a.c. but strongly ripple-modulated |
| 6 | not used | Good | Filtered tone, definite trace of ripple modulation |
| 7 | not used | Moderately string | Near pure tone, trace of ripple modulation |
| 8 | not used | Strong | Near perfect tone, slight trace of modulation |
| 9 | not used | Very strong signals | Perfect tone, no trace of ripple or modulation |