That first post under my name was posted by the moderator on my behalf (thanks!), so now it's time for me to introduce myself.
I'm Dave Cantor. I grew up in Everett, Massachusetts, which had a big pile of sulfur at the Monsanto plant which was adjacent to Everett Station, then the northern terminus of the Main Line of the BERy, now the orange line of the MBTA. I've been fascinated with rapid transit and trolley operations, and especially signalling and switching, since my mother took me on the "El" and subway into Boston when I was four years old.
But that was way more than half a century ago.
I'll lurk for a while, and then I'll probably have a few questions for the other old-timers here who remember the trolleys in and around greater Boston.