In four places RNF shows on a schematic.
Left near center by 'orange white'
Right top between circled 5 and 7,
Lower right, inside 'timer' and by 'DC in'

What is RNF supposed to mean ? Anyone knows ?
The weird image is because schematic is printed on mirror mylar film, not paper.

 

A guess.

https://www.lintechcomponents.com/product/manufacturer/19130/show

 

Perfect, thanks.
Should be near "Radio Noise Filter" then.

 

Raptor brand.
Power Noise Filter.