The most common relay is the standard non-latching type. This comprises a relay coil, an armature and switch contacts as shown in Fig,9(a). When no current flows through the coil, the relay contacts are held in their normal position by spring tension, with the IMC (normally closed) contact resting against the COM (common) contact and the normally open (NO) contact left open. Conversely, when the refay is powered, the current through the coil causes the armature to be attracted to the coil's pole piece and this moves the relay contacts to their opposite position. As a result, the COM contact closes againstthe NO contact and the NC contact opens.
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