"N_Kook"

Yes it would seem R-Core,

eg

http://www.dibao-transformer.com/Ima...ormer-30VA.png

I wonder how they are made.

** An R-core is wound with one continuous strip of steel - tapering at each
end to get a round cross section. The two plastic bobbins are made as halves
and glue together around each straight limb of the core.

There are also gear like teeth on the ends of the bobbins - allowing a
machine to spin them on the core while an operator feeds them with wire.

Then the bobbins and wire ends are secured and an overall insulation wrap
applied.

A steel claming frame is finally attached to allow chassis mounting.

Clever - huh ?


..... Phil