Andons are those papercovered squarish lights; beya is of course a heya or room. The andonbeya at the PMT is where people are always hiding from pursuers, or recovering from wounds, and where the Great Big Spoiler hangs out. I'd somehow assumed it was a store room kind of space where you kept the andons until they were needed at night.
Not, evidently. It's a windowless room where you must use an andon even during the daytime. Which is fine and good, but there in ch 1 of vol 1 we have Yosa-chan and Young Dork in the andon-beya, separately and together, standing beneath a window, not once but several times.
Unless the whole point is that there's not *supposed* to be a window in the andon-beya and it's dum-dum-dum not really there.