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Hacker News on Rails, powered by React on Rails Pro. Open the source on GitHub by ShakaCode.

Commit 06fc0df

Rendered at 11:17:12 GMT+0000 (Coordinated Universal Time) with Rails + React on Rails RSC.

One Manhattan power room took down FAA air traffic control in 1991 (matthorn.io)

48 points by spectraldrift 1d ago | 7 comments

crmd 19h ago
> Because the alarm wire carried current only during a fault, an open 25-inch strap produced the same electrical state at the receiving end as a healthy power plant.

I’m a building automation and controls tech in Manhattan, and for this exact reason digital feedback points and alarms are always normally-closed, and analog points are 4-20mA. This allows differentiation between nominal zero values and a fault in the loop.

Disasters like this are what our best practices are borne from.

radicality 17h ago
> I’m a building automation and controls tech in Manhattan

Hi - sorry if this is not your expertise, but I thought I might as well try asking. I live in ~central Manhattan, in a ~40th floor apartment with a corner view with large windows meanings lots of glass through which sound will travel. For around a year now there's been an annoying high tone coming from somewhere nearby, I would suspect perhaps some large AC fans, or maybe generator coil whine? It's persistent, around both ~2587Hz and ~2475Hz peaks, so a quite high pitched tone that's been driving me insane. The moment I open a window it's just excruciatingly "there", and even with windows shut it's still faintly there in background.

I don't know how somehow no one else has complained/gotten it fixed in this long. I'm overall use by now to manhattan noise, but this kind of persistent high pitched tone is another level of noise annoyance. I know the general direction it's coming from, and have few ideas for which buildings/devices it might be based on just seeing from my window, but pinpointing this kind of tone is difficult.

Again, might not be your expertise at all, but if you know of how I could proceed with it, to either find the source, and/or report this somehow for an investigation (311 ? some other agency? ) ? Thanks upfront!

toywinder 17h ago
I have been dealing with something very similar - I am not certain if the frequencies are in the range of what you are experiencing but I have found a device called a "Bat Detector" which is a simple circuit board that uses a directional mic array to help locate bats in dark environments. It plugs into a pair of headphones and has a frequency control knob so you can try to dial in the sound you are looking for. I don't live in an area as dense as yours but I would try mounting the detector to a tripod with some kind of sighting scope to be able to aim it with some precision.
stilldavid 17h ago
My company sells a 4-20mA sensor and I always wondered why. Thanks!
mandevil 18h ago
20 years ago some friends and I were walking by 33 Thomas St and discussed how that must be the building that they imprison Magneto in. Weird looking building.
gfat 20h ago
The overall site has a cozy feel to it. Well done
mcbishop 19h ago
This is an awesomely clear and methodical explanation of system failure.