The 103, 300 Amp contactor is a heavy duty relay. Similar to the smaller 100 amp B101 the contactor uses a single pole with double make or double break switching. Contacts are protected in a molded plastic cover. Panel mounting is standard. The powerful electromagnetic structure produces high contact pressure which results in very reliable low resistance contacts for long life. The 103 series are ideally suited for applications in telecommunications, hoist and elevator industries, rail mass transit and others.