[ Another voice. Will's been having more luck with this than expected, but each voice he hears over it is a huge relief regardless of frequency.

It's choppy, though. Will can't really begrudge someone not intuiting something as clunky as a radio with no directions printed on it. He's going to assume he understands what's being asked, however: ]

One of those buttons. Keep it pressed down while you're talking. You won't be able to listen to me while you're doing it, but you'll transmit your voice.

...I assume. [ So, by implication, this stranger should be able to tell which button is the right one, because it's going to temporarily shut off the white noise that contains other voices.

Assuming this other person's radio looks anything like the one Will's holding, anyway. ]