Relay used at telegraph receiving stations, particularly those operating on long connecting lines. Often signals received over long lines were too weak to operate the receiving instruments directly so the relay served as a very sensitive switch to connect a local battery to the receiving instruments.

A polarized relay incorporated a permanent magnet in its design. Because this type of relay depended completely on magnetic effects, it was faster and more sensitive in operation than a non-polarized relay which incoporated a mechanical return spring.

Physical Description

Two vertical wire coils and brass components on brass baseplate. Base plate and brass terminals mounted on wooden base. L-shaped magnet with one leg vertical and one leg beneath coils. Armature pivoted on vertical axis beside magnet on one side of coils and arranged to move between terminals on top of coils and between contact points on opposite side of coils.

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