Some time ago I bought a signalman with an LED red lantern in his hand to flag down a train. I have no idea who made the signalman, and if it requires DC or AC to operate correctly. So here's what I did, and what I deduce from my tests.
1. Using a 8.4V Nimh battery, the LED illuminates no matter what the polarity of the hookup.
2. Using an AC transformer and a voltmeter, the LED illuminated without any noticeable flickering, and at 12 VAC, the LED was too bright in my opinion.
I conclude that the signalman has a rectifier because the LED illuminates with AC & DC power, and the LED is not sensitive to polarity. Is this a correct assumption?
Can the signalman be powered by an isolated section of outside rail without a relay by adding a resistor to keep the current flow at 20ma? I run DCS, so the track voltage could be up to 22VAC.
Besides, a lot of my gun money is going for trains. 
I also have some AR-15's of various flavors.