Dual coil latching plug-in relays

The 255 Series is a two coil latching version of the general purpose type 219 relay. When the operate coil is momentarily energized, the energized position with the power removed from the coil. The second coil when momentarily energized, provides electrical reset of the contacts. All contacts operate from a common armature to prevent contact overlapping. Coils are rated for continuous duty.

Source: Struthers-Dunn