Wow, I hope someone knows about this and shares, I've been around a long time and I've never seen one of those. As to the nails, MILW used to have dragging equipment detectors that were simply wires nailed to one or two ties that were hooked to a light bulb, a dragging object would cut the wire and when the caboose went by the light would be out and they would have to inspect the train. Voltage on these devices varied depending on what was available and would be as little as 12 volts from the signal system to 120 volts from a nearby company well---we offed a bunch of coyotes with one of the 120 volt models--seems the train had cut the wire and before the maintainer got there to put down new wire it had killed a rabbit and when the coyotes went for the rabbit they got zapped too. Anyway, hope someone can share some info on this.