"Oh, right. No radio..." Mary lapses into silence for a while, then muses, "Cat whisker crystal detectors were the most common back home, but they can be so fiddly. And how fine a wire can we get? ...Crystal-to-crystal would probably be best, but the combination to use depends on what you can pull from the mines. I mean, I'm assuming that semi-conductors are out of our reach for the moment..."

Guess who grew up in a time when crystal radios were popular with hobbyists and scouting groups?