The picture above shows a 3000 series Relay, which is one of the standard BPO types.

The relay consists of a coil, mounted on a yoke.  Fitted to the yoke are the contact sets and finally an armature is pivoted on the front of the yoke, held in place by a locating screw or clip.

The coil is energised and this attracts the armature, which pivots on the yoke, operating the contact sets.  A simple device, but one that has hundreds of variations, due to different contact sets, coil types and armatures.

The residual stud is non-conductive and prevents the armature from remaining closed due to residual magnetism.

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Last revised: November 28, 2010