chart: SPY 4min Signals

Courtesy of TradeStation.com

Green circles are buy signals.  Two things must happen.  You need a cross over in the bottom window or the histogram to be positive and you also need a price bar to close above the cyan MA and the purple MA to cross the cyan MA in the top window.
Red circles are sell signals.  Two things must happen.  You need a cross over in the bottom window or the histogram to be negative and you also need a price bar to close below the cyan MA and the purple MA to cross the cyan MA in the top window.

Of course it is wise to use additional tools for the best confirmations and do not forget to always use protective stops.

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This has been posted for Educational Purposes Only.   Do your own work and consult with Professionals before making any investment decisions.  
Past performance is not indicative of future results.