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.
The physical plant: why signaling went to glass, what lives inside a 48-strand cable, how a midspan access works without touching the express path, and how a loss budget quietly fails at the far end of a fifty-mile corridor.
The logical plant: which devices may share a wire with vital equipment, an addressing schema that encodes the corridor into four octets, and the race between ring reconvergence and a vital processor's stale-data timer.