Instead of having a magnetic coil, a sequencer has a bimetallic disk inside that warp when exposed to heat. A bimetallic disk warps its shape because it’s made of two dissimilar metals that heat at different speeds, and it takes a little bit of time for the disk to warp. The time it takes for the thermo-disk to bow out and snap into place creates a time delay. The disk snaps and displaces the pins, causing the contacts to close. As the sequencer cools down, the pins can snap back into place and open the contacts again.