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Self-protecting (fail-safe) safety isolating transformer symbol: a shield containing two overlapping vertical circles with a horizontal line across their overlap, and a capital letter F outside the shield at its lower right
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Chargers and power adaptersConsumer electronics

Self-protecting (fail-safe) safety isolating transformer

A shield containing two overlapping vertical circles with a horizontal line across their overlap, and a capital letter F outside the shield at its lower right. · also called “F transformer symbol”, “fail-safe transformer”, “safety isolating transformer F”, “self-protecting transformer”

What the Self-protecting (fail-safe) safety isolating transformer symbol means

Self-protecting safety isolating transformer

The letter F next to the safety isolating transformer shield marks a self-protecting (fail-safe) safety isolating transformer under the EN 61558 series. Without the F the shield is a plain safety isolating transformer; a small box under the circles instead means short-circuit-proof.

Source · Official website Noratel transformer symbols and standards reference sheet · checked

Where it appears

Chargers and power adapters
  • EN 61558
    —This meaning

Questions about the Self-protecting (fail-safe) safety isolating transformer symbol

What does the Self-protecting (fail-safe) safety isolating transformer symbol mean?
The letter F next to the safety isolating transformer shield marks a self-protecting (fail-safe) safety isolating transformer under the EN 61558 series. Without the F the shield is a plain safety isolating transformer; a small box under the circles instead means short-circuit-proof.
What does the Self-protecting (fail-safe) safety isolating transformer symbol look like?
A shield containing two overlapping vertical circles with a horizontal line across their overlap, and a capital letter F outside the shield at its lower right. It is also called “F transformer symbol”, “fail-safe transformer”, “safety isolating transformer F” and “self-protecting transformer”.
Which standard defines the Self-protecting (fail-safe) safety isolating transformer symbol?
It follows EN 61558.

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