What is "electronic explosive detection technology"?

What is "electronic explosive detection technology"?

In the Aviation and Transportation Security Act of 2001--the legislation that created our agency--congress called for the TSA to be able to screen all checked bags, using explosive detection technology. There are two types of explosive detection technology; it's basically technology that screens for explosives: Explosive Trace Detection Systems, which screen for traces of explosives; and Explosive Detection Systems, which have often been referred to as the "minivan multimillion dollar machines" that are sitting in the lobbies of our airports. They work similar to a CAT-scan machine, where you put a bag into it and it screens for explosives.