The True Strength Index (TSI) is a momentum oscillator that ranges between limits of -100 and +100 and has a base value of 0. Momentum is positive when the oscillator is positive (pointing to a bullish market bias) and vice versa. It was developed William Blau and consists of 2 lines: the index line and an exponential moving average of the TSI, called the signal line. Traders may look for any of the following 5 types of conditions: overbought, oversold, centerline crossover, divergence and signal line crossover. The indicator is often used in combination with other signals.