Tom Ervin, Professor of Music, University of Arizona tells this story:

I had purchased a talking metronome while I was attending a conference in New York for music teachers. Before my son and I boarded our flight home, I hefted my carry-on bag onto the security-check conveyor belt.

The guard's eyes widened as he watched the monitor. He asked what I had in the bag, then slowly pulled out the six-by-three-i…