Interesting. Two long and two short for a grade crossing. Then they started holding the lanyard on the last one until the middle of the crossing. Things evolve.
What amazes me about old products is the fact that so many of them say 'made in Chicago'. So many old books and random things you wouldn't expect say made in Chicago. It really was the city of big shoulders. Is it weird to be nostalgic for the 1900-1930 era US? I wish I could have seen the era of the great engineers and famous designers. These days, everything is just credited to a faceless corporation. It would have been amazing to go to Chicago and see all the rail yards and industries. Looking through old pamphlets and papers like this really shows how much has changed. So much is gone, and I think Chicago lost a lot of its glory with the fall of the railroads in the postwar years.
It's funny how little has changed over the years. On a daily basis we use a lot fewer of these, but those still used haven't changed much (the grade crossing signal acptulsa pointed out is a good example).
Some of the whistle signals changed in the early 1900's when air brakes and knuckle couplers were mandated. Prior to that, with no air brakes and link and pin couplers, trains could break in two and the engine wouldn't necessarily know it. The rule books contained a couple pages of rules on what to do if you got to a station and found out you were missing part of your train or if you found the rear end of a train sitting on the main track. Once air brakes became standard that problem went away because when the train parted, the brakes went in emergency and the engine was immediately aware, plus the brakes were applied on the detached portion. That's what the three long whistles for "train parted" is about. If you look in a "modern" (post WW1) rule book, that signal isn't in the rules anymore.
