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Value | 1936 definition | modern definition |
---|---|---|
1 | Extremely rough hissing note | Sixty cycle a.c or less, very rough and broad |
2 | Very rough a.c. note, no trace of musicality | Very rough a.c., very harsh and broad |
3 | Rough, low-pitched a.c. note, slightly musical | Rough a.c. tone, rectified but not filtered |
4 | Rather rough a.c. note, moderately musical | Rough note, some trace of filtering |
5 | Musically modulated note | Filtered rectified a.c. but strongly ripple-modulated |
6 | Modulated note, slight trace of whistle | Filtered tone, definite trace of ripple modulation |
7 | Near d.c. note, smooth ripple | Near pure tone, trace of ripple modulation |
8 | Good d.c. note, just a trace of ripple | Near perfect tone, slight trace of modulation |
9 | Purest d.c. note | Perfect tone, no trace of ripple or modulation of any kind |
If there are other notable tonal qualities add one or more of the letters A–X, listed below, after the number. |