Harris, Tom. “How Burglar Alarms Work: Breaking the Circuit.” How Stuff Works, Inc. Media Network: A Convex Company. 15 Mar 2006. http://home.howstuffworks.com/burglar-alarm1.htm Brian, Marshall. “How Relays Work: Relay Construction.” How Stuff Works, Inc. Media Network: A Convex Company. 15 Mar 2006. http://electronics.howstuffworks.com/relay1.htm Brian, Marshall. “How Electromagnets Work.” How Stuff Works, Inc. Media Network: A Convex Company. 15 Mar 2006. http://science.howstuffworks.com/electromagnet.htm