If you're not a trolley car nut you probably have no idea what this picture is about. The simple answer is we had a full moon last night at Orange Empire Railway Museum. But so did everybody else on earth. So what about the five light bulbs. Well the trolley wire is at 600 Volts. The light bulbs are 120 Volt bulbs. 5 times 120 equals 600. So if you string 5 of these light bulbs in series between the 600 Volt trolley wire and ground (the rails) the bulbs will light if the power is on and not light if it is off.

But there is a glitch. What if one light bulb burns out? Like with the cheap mini-Christmas tree lights, the other bulbs go off too because the burned out bulb presents a gap and no current can flow. In other words, the power could be on but the bulbs not lit. Oh, getting across 600 Volts is usually a one time deal.

Hope you like the picture.