From Mladen Rakic:

Theory:

The original indicator was described by B. Williams as fourth dimension - Trading Zone:

If the current bars of AC and AO are trending up, it shows that the zone is up
If the current bars of АС and АО down, it shows that the zone is down.
If the bars of AC and AO are differently directed then the bar is colored grey.
This version:

The indicator is based on the following 3 indicators:

Heiken Ashi
smoothed (if the smoothing period is >1)
regular (if the smoothing period is <=1)
Accelerator Oscillator.
Awesome Oscillator.
Comparing the slope of the smoothed Heiken ashi can filter out some of the false signals. The combined states and values of the 3 are producing zones and trade signals. This version is adding the smoothing possibility using one of the 4 average types :

simple moving average
exponential moving average
smoothed moving average
linear weighted moving average