What do the symbols for components L1 (FB) and MV1 mean in the schematics below?

What does MV and FB mean?



2 Answers 2


MV1 is a Metal Oxide Varistor (or MOV), sometimes called a Voltage Dependent Resistor (VDR). See Wiki. It is used to protect the rest of the circuit from high voltage transients and surges that would otherwise cause damage. The 220V rating of MV1 is usually the AC voltage rating of the varistor. It is the AC voltage at which the varistor has no effect. A transient voltage above this value will cause it to conduct and clamp the transient to a safer value. There are lots of other parameters of a varistor (energy rating, maximum current, etc) which are not specified on your schematic. You can also see on your schematic that for 220V operation the value of the varistor has been changed to 390V.

FB1 is a ferrite bead. Wiki. This acts to filter out very high frequency noise or interference. A ferrite bead is usually specified as having a certain impedance at a certain frequency, such as 100 Ohms @ 100MHz.


based on the connection and the letters, MV - Metal Oxide Varistor, L1 - Ferrite Bead. Correct me if i am wrong.

  • \$\begingroup\$ Heh I was going to say SIDAC but MOV is more correct. \$\endgroup\$
    – Bradman175
    Commented Aug 3, 2016 at 9:25

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