I refer you to an absolutely stunning gallery of 227 photos of torpedoboat operations by the Kaiser's navy in WW1:
http://www.dreadnoughtproject.org/gallery/Halbflotille-XI/p08_e
Regarding this specific photo, and as one who has modeled warships but never served on one, my question is this: What are the circular devices on the mainmast above the stack (and the semi-circular device on the aft mast, presumably)? Are they RDF of some sort?
Thanks in advance.
Greg