See the screenshot which is from John Ehlers book "Cybernetic analysis for Stocks and Futures".
The important point is that, when the filter line is used in conjunction with Laguerre RSI, then make sure that the Gamma have the same setting for both indicators.
The rule of thumb using the filter line is:
Trade only long if price is above the filter line when Laguerre RSI crosses above the threshold (0.15). Trade only short if price is below the filter line when Laguerre RSI crosses below the threshold (0.85 or whatever settings You use for Your trading).
http://forex-indicators.net/mt4-indicators/laguerre-rsi
Thanks for starting this great thread Capito.
Cheers
Tomas