Switch tower operation

GREAT question! Hopefully, one of the knowledgeable rails here will help us! ☺

Hope we get a definitive explanation.

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Big levers, long rods and sturdy bell cranks.

And some real grease at the link points!  

The rods seem to be supported every so often.  Were grooved wheels used?

Grooved rollers (wheels)? yes.  I remember visiting the major crossing south of downtown  Chicago (toward Midway Airport, can't remember the neighborhood's name) and watching an operator in a small shack the pull levers  for the old semaphores controlling five, maybe six, intersecting  tracks. You could hear the rods and levers and the old signals squeaking as trains approached on the horizon. And talk about traffic! What a great piece of working history! Alas this all changed about ten years ago.  

THANKS for the informative info!  ☺

Thanks, loved the pictures, it looks like a Rube Goldberg, but it must of worked given how long these were in operation. Makes me almost want to put manual turnouts on my layout and create something similar (almost)