Bunnell Polar Relays

13A       Polarized relays come in many shapes and sizes, but the one thing they have in common is a permanent magnet. In the usual construction, the electromagnets are mounted at one end (pole) of the permanent magnet. The armature of the relay is pivoted from the other pole of the permanent magnet so that its far end may swing between the cores of the electromagnet.

      With no electricity flowing in the electromagnet, its core will be equal magnetic polarity and opposite that of the relay armature. The armature will be equally to the cores.

      However, when the circuit is in operation, the current through the electromagnet induces magnetism in its core which either aids or impedes that caused by the permanent magnet. The armature will then be attracted to on ecore or the other, depending on the direction of the current. As the diection of the current changes to indicate marks or spaces of information, the armature swings between the cores and this between the relay contact and stop.

13B      This style of polarized relay does not require a seperate contact stand. All of the components are attached to the permanent magnet.

      Both of the relays shown here utilize series-wound electromagnets and may be used, for example, in diplex circuits, or in any circuit where a sensitive relay is required. Differently-wound polar relays are recognizable by the additional coil wire termincals in the base.