The signal line of the MACD (Moving Average Convergence/Divergence) indicator is often used as a momentum filter in auto trading algorithms.

• Enable buy logic only when the signal line is above the 0 level and the last "bar" of the signal line closes higher than the previous "bar" of the signal line (this inherently includes upward level crossovers).
• Enable sell logic only when the signal line is below the 0 level and the last "bar" of the signal line closes lower than the previous "bar" of the signal line (this inherently includes downward level crossovers).