Wallwarts

The 230v and low voltage are indeed separate but the devices do have a fuse in them. It is usually a non resettable combination thermal and overcurrent fuse embedded in the primary winding wrapping.

The fuse in the plug is only to protect the cordset.

They have thermal protection. This permits the differentiation of power leaving the device in normal operation from power being dissipated in a defective transformer.

DG

Sigh. The plug fuse is not to protect the ring but *solely* the flex to the appliance it feeds.

If the 230 volt winding was touching the 12 volt winding it would not be

The primary winding in the transformer of a wall wart has a non replacable thermal fuse built in to it. This will allow short term overloads of the secondary before rupturing. Regulated DC supplies usually incorporate electronic overload protection.

Please eff off as you are an idiot.

There are/were also a few warts with a wire link as a fuse and nowt else. I doubt they meet requirements for UK equipment, as there's no fire protection, but they exist. Probably imports from Oman or something.

NT

I think perhaps the OP has noticed that the transformer has split-bobbin construction and is not suggesting that transformers are wound from uninsulated wire...

Not met the OP before then?