Jan. 24, 2007 - Why is the Bush administration escalating its accusations that Iran is backing Shiite extremists inside Iraq? One reason: mounting intelligence indicating Tehran has been supplying insurgents with electronic sensors that trigger roadside bombs used against U.S. troops. The devices in question—which cost as little as $1 a piece—are called "passive infrared" sensors or detectors. They are commonly used to turn on lights or burglar alarms when someone or something passes in front of them. Over the past year, U.S. forces in Iraq have repeatedly fallen victim to sophisticated homemade bombs—known as IEDs, or improvised explosive devices—which...