The Elliptical Lock Up is a double break bit with a "locked" lozenge in the center. It is stronger than the Control Plate due to it having a smaller surface area. Consequently, a horse using his tongue as a means of pushing against the bit and therefore taking control, will draw back and tuck his chin in, coming back to a better point of control.
By Locking up the Elliptical joint, it removes any nutcracker action, meaning it will bear less pressure on the horse's bars. It in turn applies more tongue pressure than the Ported Kernel making it a stronger bit.