Two overlapping circles (isolating transformer)
The product is, or contains, a transformer of the isolation type: its output is electrically separated from its input.
Symbol reference: IEC 60417-5221
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, with a horizontal line through the middle and no shield around them.
- Who may apply it
- The transformer or power-supply maker. A letter F beside it marks a fail-safe type.
What it does not promise
Without the shield outline it is not the safety isolating transformer symbol (5222). 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 5221 (title, function, notes) — Symbol 5221 from IEC 60417, “Isolating transformer, general”: to identify a transformer of the isolation type; the letter F may be used adjacent to indicate a fail-safe function. Checked 2026-09-24.
- Wikimedia Commons: File page transcribing IEC 60417 entry 5222 (title, function, notes) — Symbol 5222 from IEC 60417 is the separate “Safety isolating transformer, general” and lists 5221 under “See also”. Checked 2026-09-24.
Written in our own words; quotations are the sources’ wording.