Their 100 y/o hardware is built from stuff that's still produced though. We still make relays (not identical ones but ones that perform the same function), wires, and mechanical levers. The system's behavior is not encoded in the relays but in the connections between them. If you had a CPU made of separate transistors you could replace burned out transistors with any future transistors but if you had one made of chips you'd need those exact chips that were out of production.

Replacing the relays in old telephone switches is a problem because they use so many weirdly specific types of relays - but those systems are only found in museums now. I believe track control uses fairly ordinary DPDT, etc., relay designs.

> If it's not broken, don't fix it.

I understand that way of thinking for a small business computer system. Not for a critical infrastructure. Also if people actually thought about like that we would still be in stone age, like why invent something new or use a new technology? Keep on using rocks to crack nuts and kill animals

I think you can imagine the difference between “I did some work and made this thing that is clearly better, but we might have a few kinks to work out” and “I did some work, and if I did it perfectly, it’s just as good as the old thing, but we might have a few kinks to work out.”

I agree with you. First, "broken" is not a binary, it might not be broken but it might not work well either. Second, sooner or later everything breaks, and you better be ready for when that happens.

But similar reasoning is why Canadian trams are worse than other countries, and it's not "good experienced engineering". In this nearly hour long rant by NotJustBikes[1] the section I've linked is about the technology and how the transit authority will not move on from 100 year old track technology which makes everything worse for customers. There are junctions where tram drivers have to stop and look at the track to make sure the junction is correctly set because the single-point switching is less reliable than modern designs. Or the driver has to stop the tram and get out to use a stick to move the track and change the junction because they aren't electrified. And then pass through junctions as slowly as 10km/h because the old track design has higher risk of derailment than modern designs.

The designs for the electrified track switches were made by one company which was sold, re-sold, and then burned down and the designs lost, and there isn't anywhere else to buy them because nowhere else uses such old track design anymore, so not only is Toronto struggling to buy parts to continue electrifying the manual junctions, it's struggling to custom-make enough replacement parts to keep the aging electric switches working faster than they fail.

And they were using trolley poles to connect to the overhead power lines instead of Pantographs until 2017, 50-100 years after everywhere else, which meant a) they couldn't get enough power through them to run air conditioning, and b) they are more likely to fall off the power line and the tram stops and the driver has to get out and reconnect them, and c) their newer trams now have to have custom dual-power connections to go through older parts of the network, and d) the carbon shoes on the trolley poles wear out quicker which means the trams are dirtier and taken out of service for maintenance more often in the wet which is when people want to use trams more.

[1] https://youtu.be/HhQxNHrD6fA?t=2311

OK, but the context here is IT in mission critical infrastructure, like energy or banking. These industries will not jump on the latest technology and will drag their feet for as long as possible, and for good reasons.

Also, I happen to be familiar with NotJustBikes, watch regularly. I don't see this as the same kind of problem. What you explained is clearly BROKE. What we're talking about works just fine and migration to newer technology doesn't provide advantages outside easier maintenance. It can't be justifies by costs, either.

A friend discovered that one of the more modern pieces of equipment instrumenting those old signals was an ancient WYSE terminal from the late 90s that had been bricked over during a station project.

They moved a booth or something and the compartment it was stuffed in was missed during the cleanout. The thing was working for at least 20 years and may still be there!

I worked with a client that had a cash disbursement system working on an ancient dBase 16-bit application. They had a very difficult to change process that required multiple transactions because the system couldn't represent the dollar amounts appropriately.