> What prevents new signals from being backwards compatible with the old system? Nothing, of course, despite the naysayers. You wouldn't, initially, try to rep

> What prevents new signals from being backwards compatible with the old system? Nothing, of course, despite the naysayers. You wouldn't, initially, try to replace - just augment; record and report the inputs and be a test-bed for the eventual digital replacement. In this case, because the originals are physical switches, it'd be more like a modern-machined duplicate of the original with a micro-controller stuck on the side. The data it would send be immediately helpful for arrival timers and such.