[Bunker]

I bought a speaker for an iPod that was about $5 or $10. Then for a club layout last year, I recorded clacker-type telegraph key sounds with a long pause and had it run in a loop for inside my "Wanamaker" depot. I actually found a translator online to send in code and actual message for anyone who could understand Morse code. Inside the large agricultural hall the sound resonated quite a distance, I turned it down after hearing it on the other side of the room. FWIW