OK, I'm having one of those days... It's not a tensioner, it's not stitch length, and it looks like a straight stitch machine... What the heck is the dial on the front by the needle? It appears to have left and right arrows, so I don't think it's a light.
I know when someone says "it's XYZ!" I'll feel like a dummy, but...?
I vote light as well. It looks like arrows, but I think it's actually (big dot)ON OFF(big dot). The dots are just so big, they look like arrowheads next to the tiny writing.
That's a cute machine. Too bad they want so much for it; I don't have a 15 clone, and that one is definitely speaking to me.