I was cleaning out a shed today and found some old Swedish Jan footsnares.
They were made for foot snaring fox in deep snow in Sweden.I remember catching a couple cats in them back in the late 70's.I just tried them out but never used them as I preferred to neck snare and not have to mess around dispatching live animals.

I've never seen one until now.

How is it powered? Is there an in-line spring inside ?

Yes a very powerful coil spring.It is adjustable inside the tube.The pan is separate(but attached with a cable so not to be lost after firing).The pan has a pin that goes in a small hole in the bottom of the tube that releases the spring when the pan is stepped on.Very simple effective design from years ago.The snare cable is sheathed so no kinks-it is multi use.
It never seen much use here-since it is a live holding device thus not efficient in the north country.Trappers here preferred neck snares and bodygrips (lethal methods)for efficiency on more remote lines.
They seemed to be popular in the more populated north countries like Scandinavia where checking every day is not a problem like it is in large more remote traplines of northern Canada.

How is it staked down or otherwise secured Boco?

Looks like a ketch-all pole but in reverse.

There is a loop on the end of the wire that is attached to the snare.The snare itself is attached to the pan after passing thru the butt end of the tube.

So you would have to pull the cable to reset and then engage the pan pin to reset the snare. Seems that It could have been about 18" shorter and still would have worked just fine.
Neat Idea though.

Boco don't go giving Wolfdog any more ideas. LOL

Interesting concept but I don't see advantage over steeltraps. Probably preceded such. Maybe a ramsnare turned on its side would serve the same purpose (and be a legal replacement for cable restraints?).

been following this tread since it started. has me very interested because there is about six or seven variations of this type of of trap but still havent gotten around to building anything similar.seeing a few problems with this right off the bat though. very interesting however

The Jan footsnare has been around for a very long time.
It is made for footsnaring canines in deep snow.A blind trail set in a track.
You just approach the trail from the side and lay the set snare right in the track.
Seen pictures of large fox catches in Scandinavia with the Jan.
The only problem with it is that it is a live holding device like a foothold trap.

Actually a neat Idea. Stand back and run that thing into the snow till the loop Is around an existing track.

Found another one today,made in Finland,tube made of fibreglass and the pan looks to be heavy duty lexan.It is a larger model,likely made for wolf.Spring is stronger too