What does "FB" mean? I can only guess it's some kind of protective device because of F, like with FU for fuse.

Is there any comprehensive online guide for such kind of symbols?

  • 1
    \$\begingroup\$ Can you provide an example schematic? \$\endgroup\$
    – Renan
    Jul 11, 2013 at 14:39
  • 1
    \$\begingroup\$ This symbol was on power source board. The device itself is small black ("metallic") cylinder without any visible signs on it. There were 3 of them. \$\endgroup\$
    – Roman Susi
    Jul 11, 2013 at 14:42
  • \$\begingroup\$ Can you provide image? \$\endgroup\$
    – user107801
    Jul 1, 2016 at 19:18

2 Answers 2


From your description, sounds like an abbreviation for Ferrite Bead.

  • \$\begingroup\$ There is no other explanation. Its magnetic, resistance is minimal in both directions, appears among jumpers, color is right. And it is also protective device. Thanks. \$\endgroup\$
    – Roman Susi
    Jul 11, 2013 at 14:55

FB is the designator for a ferrite bead. A FB acts a lot like an inductor, in that it filters out AC, and they slow transition of DC signals.

Best list of designators I've run across is in Wikipedia.


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