Never trust a system that seems to be working

Post by smoochy » Mon, Oct 17, 2022, 9:19 PM UTC

reaperducer wrote: post #199

usrbinenv wrote: post #88

A bit of an off-topic: I only ever saw white traffic lights in the US and Canada (specifically, pedestrian traffic lights) and they confused me a lot at first - the rest of the world uses green. The icons displayed (hands) are confusing too: the rest of the world uses an icon of a man walking or standing.

the rest of the world uses green. Only if you define the rest of the world to mean the very small percentage of places in the world you have been. From Wikipedia: In some countries, instead of "don't walk", a depiction of a red man or hand indicating when not to cross, the drawing of the person crossing appears with an "X" drawn over it. Some countries around the Baltic Sea in Scandinavia duplicate the red light. Ins…

Post by righttoolforjob » Mon, Oct 17, 2022, 9:21 PM UTC

mlazos wrote: post #177

It’s really interesting how factorio problems are pretty much the same as multiprocessing/distributed systems problems. It just shows how universal and fundamental the idea of “work” and “workers” are. An engineer on my old team came up with a credit system to solve this problem, the receiver issues credits to the sender, which only sends when there is a credit available - this ends up with the same better failure mo…

Post by ddingus » Mon, Oct 17, 2022, 9:25 PM UTC

Gordonjcp wrote: post #243

bombcar wrote: post #127

Earlier quoted context omitted.

Yeah, any design is going to be various trade-offs, and you have to understand them (and how they may relate to your mission) when determining what to do and what would be a bad decision. For example, cars have "fail open" brakes but have independent cylinders so that it is relatively hard to have all four wheels fail at the same time (older cars had single master cylinders) - and one of the tradeoffs is that people…

Pretty much every car made since the 1980s has had dual-circuit brakes with usually one front and one rear wheel cylinder on each circuit. Volvo being Volvo took it further with their 2-series cars in the 1970s and 1980s, where the front discs had four-pot calipers configured as two sets of two-pot calipers. Each braking circuit had one half of each front caliper and one rear caliper, so in the event of one half of t…

Post by TeeMassive » Mon, Oct 17, 2022, 9:33 PM UTC

Karellen wrote: post #10

One reply tweet notes "a complex system always operates in a failure state", but to find more discussion on this point it's worth noting that this is a restatement of: > "The Fundamental Failure-Mode Theorem (F.F.T.): complex systems usually operate in a failure mode." -- John Gall, General Systemantics (aka Systemantics , aka The Systems Bible ), 1977 https://en.wikipedia.org/wiki/Systemantics > Searching for "funda…

Post by sneak » Mon, Oct 17, 2022, 9:36 PM UTC

mananaysiempre wrote: post #156

electroly wrote: post #43

This is why 4-20 mA is a common signaling standard in industrial automation. 4 mA means zero and 20 mA means one. 0 mA means broken transmitter !

Also why a standard keyboard has a Break key: used to be that a telegraph station would have a bell that rang if it detected a broken connection (a “break condition”), then people figured that deliberately inducing a break was a handy way to alert the remote operator. I think the first automated telegraph systems actually used current-loop signalling, but I’m not sure about the first practical ones; in any case, the…