When near, intermediate & far period relative strengths get into sync just like moving averages, it shows maximum trend strength.
lets say ... near rs crosses 0... 1pt interm also crosses 0... 2pts far also crosses 0... 3pts i use 10 21 55 time periodes which are selected as they will be in sync with my Rsi indicator settings of 10 21 rsi crossover.
Disclaimer: it's just educational purpose about Relative strength and link between different time periods.