It's a KDJ indicator. SP index takes 45 cycles (nearly three months), so the signal is more reliable;

The original "SP" indicator has only one line, as the saying goes: one is point, the other is surface, and the third is solid;

According to this idea, it was changed to three lines, namely

Short, medium and long term,

When all three lines are in the low position (so-called resonance), the buy signal is more reliable, and the problem of low passivation of the original SP index can also be avoided.

Similarly, when the third line is at a high level, sell it.

Actually, there are not many indicators. If you can really understand and use them well, one indicator is enough.