"So once the network's fully characterized, I start setting off the signal pulses. I let the network know"-he tapped his glasses and the virtual control interface that only he could see-"exactly what signal I'm about to send, then trigger it. The net records all the responses it can, I hit it with another pulse; maybe change modes, it starts building up a rough picture. I examine it, see if I've got something coming up. Maybe I go back, do a few more GPR or radio shots, or try another acoustic signal, or shift frequencies. Eventually, I've got all the data I think will be useful. Then I can really go to town on this stuff; sensor fusion, bandpass filtering, synthetic aperture, Kalman and Weiner filters, all that kind of thing, plus some tricks of my own.

"With a handful of these motes and no special signal generators, I can use the ambient sound to locate and determine the number, direction, and general composition of your tents-without any of my dust motes actually touching the tents. Heck, with equipment twenty years older, I could send any two of you off to have a conversation, and not only locate you, but pick out your entire conversation, whispered, on the other side of a hill three hundred meters off. These motes have access to my own neural net code, expert systems, fuzzy logic structures, all sorts of stuff in the control unit and local heavy-duty processors, like in the main control unit here."

He patted another simple metallic box on his belt. "Give me powerful signal sources, and I'll guarantee to map out anything you want, above or below ground. And in this case, I'll even guarantee that you'll have enough detail to count teeth in a skull."

"Can you keep a record of how you produce the results?" Helen asked.