The Siemens polarized relay shown consists of an armature "a", pivoted at one end "h" in a slot at one end N of a permanent magnet "m", the other pole "s" of which is fixed to the yoke "y" of a horse-shoe electromagnet M. The armature is placed Polarized relays. between the poles of the electromagnet, and being magnetized by the magnet "m" it will oscillate to the right or left under the action of the poles of the electromagnet M according as the current passes through M in one direction or the other.