My Pfaff Quilt Expression bought Dec.30, 2002 has a signal that shows on the "window" when the bobbin has about 5 yards of thread left on the bobbin. FIY, this will only work when the cover to the bobbin case assembly is closed!!!
I remember the purchase date because I LOVE my machine, it has so many features that take the hassle out of garment/quilt/craft stitching. These were features I wasn't even looking for, especially the needle down thing.