Randy becomes almost certain that if he could unlock that filing cabinet, he would find some electronic gear inside it. Directly underneath his laptop there is probably an antenna to pick up Van Eck signals emanating from the screen. Below that, there is some gear to translate those signals into a digital form and transmit the results to a listening station nearby, probably right on the other side of one of these walls. Down in the bottom are probably some batteries to make it all run. He rocks the cabinet back and forth as much as the chains will allow, and finds that it is indeed rather bottom-heavy, as if there’s a car battery sitting in the bottom drawer. Or maybe it’s just his imagination. Maybe they are letting him have his laptop just because they are nice guys.