A signal on the fixed-block system, at right, which is in use throughout much of the subway system. Shutterstock Of all the stock excuses given to explain a stalled train or a delay in service on the ...

A sensor signal conditioner (SSC) is an integrated circuit that improves — or conditions — the signal coming from a sensor to reduce noise. The SSC also converts the signal from analog to digital ...

Deep inside a subway station in Brooklyn, in a cramped, industrial room, Dyanesha Pryor pushes in a metal lever on a hulking machine that was installed nearly a century ago. A few hundred feet away, a ...