Theory :
In “Recursive Median Filters” in March 2018 issue of TASC, author John Ehlers presents an approach for filtering out extreme price and volume data that can throw off typical averaging calculations. Ehlers goes on to present a novel oscillator using this technique, comparing its response to the well-known RSI. He notes that by being able to smooth the data with the least amount of lag, the recursive median oscillator may give the trader a better view of the bigger picture.
Usage :
Ehlers suggests usage as signals on zero line cross. You can use it that way, but you can also use the slope change too.
PS:
Indicator is using default parameters as specified in the original. But you might want to experiment with that and using longer high pass periods seems to produce interesting results (as in the example)