Miniatronics Roof Top Flasher Beacon part number 100-001-01
Here is a nice circuit for use as a roof top flasher on an emergency vehicle or maintenance of way caboose or other railcar. Although the package is labeled as HO scale it can realistically be used for O scale applications. The circuit must be powered by an external AC or DC source up to 14 volts. A nine volt battery can be used without the need to have track pickups.
The amber L.E.D. (3mm) mimics a real flashing light. If used as a rooftop beacon the included lens cap will diffuse the light. Drill an 11/64" hole for the lens cap. The LED snaps into the lens.