Hi gang , in all my many years involving trains I never quite understood just what is happening when the tower man goes trackside and hands a moving loco orders via the pole and string nabbed by fireman or engineer..I understand what's happening physically (pole lifts order on string up to cab/arm snatches string/order spanning the VEE, etc.). What I never got is, what do these messages/orders say ? I.E. Why doesn't crew know all their set-outs and pick-ups at time of departure from where train was first made up ? What, therefore is it they need to know in the middle of the run ? Is it merely that a new order from a client at a spur/industry along the route just a few minutes earlier contacted RR for, say, a pickup of an empty or load which wasn't in original orders at departure ? Did I just answer my own question ? And why couldn't it have been radioed directly to conductor in caboose ( in 1950's and later radio-communication methods ) ?