I was surprised, last week, to find one of my electronic concepts in the home of a banker: a random doorbell. I designed a few embodiments of this concept -- as best I know, I was the first. One went into production as a kit in Australia in 2002. It was billed as the Raucous Alarm, and they promoted it with the line: "It sounds so dreadful, that you cannot ignore it." I thought it played some nice little tunes, myself. Every time one pressed the button, my random doorbell played a melody that the world had never heard before. OBSERVATION: I would think it likely that the banker's doorbell now has a little computer inside (a microcontroller). Mine used common off-the-shelf components.