1, The Relative Strength Index compares periods with up closes with periods that have down closes to produce an index reading reflecting the strength of price changes on a scale of 0 to 100. The index provides overbought or oversold signals, and divergence/convergence with prices is an important part of the analysis.
2, A popular oscillator developed by Welles Wilder, Jr. and described in his self-published 1978 book “New Concepts in Technical Trading Systems”. RSI is plotted on a vertical scale from 0 to 100. Values above 70 are considered overbought and values below 30, oversold. When prices are over 70 or below 30 and diverge from price action, a warning is given of a possible trend reversal.