Thirty-three years of notebooks and counting. Ask me why the British loading gauge is the way it is and cancel your afternoon.
Open question to start us off: what got you in? For me it was signalling — the realisation that the whole network is a giant distributed state machine made of relays and rules, designed so that failures land on the safe side. Absolute block working is one of the most beautiful protocols ever designed and it predates computers by a century.
not a train person myself but "giant distributed state machine designed to fail safe" is the single best sales pitch I've ever heard for a hobby. go on then, what's a token?
Delighted you asked. Single-track lines: only one train may occupy the section, so possession of a physical object — the token — IS the permission to enter it. One token per section, handed driver to signaller. You cannot have a head-on collision if there is only one key to the room. Mutual exclusion, implemented in brass, 1889.