Coffee from hell

At the beginning of the shift today, I put on a radio and walked over to the hospital residence to try out the lab tech’s new espresso machine. As soon as I plugged it in, it broke out in an unearthly anguished howling. Taking the noise for an alarm, I pulled the plug, fiddled with a couple of bells and a whistle, and tried again. Cue the apocalypse. But was the noise actually coming from the espresso machine? I looked up at the startled but battle-ready faces of my cohorts in the dining room. I looked down at my belt. The cause was suddenly clear, and with a flick of the wrist I returned the fabric of the universe to its proper state. “Hey guys… Guess what frequency the espresso machine broadcasts on.”