This Indicator is based on the classical indicator ‎"Relative Strength Index".

IT draws 2 lines: 

• Main blue line with input parameter RSIPeriod.
• Signal red line.

Buy when the main line (Blue) falls below a specific level = 30 and then rises above that level and main line rises above the signal line (Red).

Sell when the main line (Blue) rises above a specific level = 70 and then falls below that level and main line falls below the signal line (Red).