About: http://webisa.webdatacommons.org/140220418

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	Only by an opposing electromagnet actively keeping them apart do they remain open, so in a power outage or other emergency, they automatically engage.
http://www.w3.org/ns/prov#wasQuotedFrom	wisegeek.com