Two circles in a shield (safety isolating transformer)
The product is, or contains, a safety isolating transformer. The IEC lists it separately from the plain isolating transformer (5221), which has no shield outline.
Symbol reference: IEC 60417-5222
A mark tells you what the maker declares, never that the product is safe.
- What it looks like
- Two overlapping circles, one above the other and split by a horizontal line, inside a shield-shaped outline. A letter F next to it marks a fail-safe type.
- Who may apply it
- The transformer or power-supply maker. The IEC note allows the letter F beside the symbol to show a fail-safe function.
What it does not promise
It speaks for the transformer, not for the product plugged into it, and it gives no output voltage or power: read the rating printed beside it.
Other marks with the same shapes
Sources
Each page below was fetched and read on the date shown. Where a symbol’s IEC 60417 or ISO 7000 number is given, a public page listing that number is among them.
- Wikimedia Commons: File page transcribing IEC 60417 entry 5222 (title, function, notes) — Symbol 5222 from IEC 60417, “Safety isolating transformer, general”: to identify a safety isolating transformer; to indicate a fail-safe function, the letter F may be used adjacent to the symbol. Checked 2026-09-24.
Written in our own words; quotations are the sources’ wording.