These Toroid Ferrite cores are useful for suppressing EMI/RFI. Applications range from audio/video equipment wiring, R/C installations, and much more. Material is similar to Fair-Rite T75; For more details, please click the data sheet link below.
Outside diameter is 0.8 inch (20mm) and inside diameter is 0.39 inch (10mm). A tough epoxy conformal coating helps reduce breakage. Colors may vary (blue, white, or black).
For typical common mode EMI/RFI suppression all you need to do is wrap several turns of cable around the bobbin shaped core. Generally speaking, more turns = more suppression. These aren't effective in every electrical noise situation, but they are the first line of defense when EMI/RFI problems are encountered.
The photo below shows a typical example of a 3-wire R/C servo cable that has a Toroid installed on it.
Toroid Data Sheet: Click Me.
