Cab signaling puts the wayside aspect in front of the engineer and enforces it. A technical theory of operation of the UltraCab II onboard unit: the DSP receiver that turns rail current into a code, the vital computer that turns a code into braking decisions, and the layered design that makes one processor trustworthy enough to hold the brakes off.
Harmon Industries started in 1946 as one man's radio shop in Independence, Missouri. Fifty-four years later GE paid about $425 million for it. The story of the hotbox relays, crossing predictors, coded track circuits and cab signals that got it there, and of the product lines that still carry its work under KB Signaling.
A room full of vital relays fails safe because gravity drops the armature when the current stops. So when you replace that room with a single processor, the only question that matters is: where did gravity go? A technical theory of operation of the ElectroLogIXS platform, from power-on to a running control point.
A three-part series on the fiber plant beneath modern railroad signaling: where the cable physically runs, how the network on it talks, and who keeps the record true. One corridor, carried through all three parts.