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Neighbor's house alarm triggers when I put my car in reverse

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Re: Neighbor's house alarm triggers when I put my car in reverse

#211

Post by DonHopkins »

_Nat_ wrote: post #170
alister wrote: post #45

Earlier quoted context omitted.

> Someone explained it properly That's a hypothesis, a very good hypothesis, but the Reddit thread and Hacker News offer many other reasonable-sounding hypotheses. I can't tell you the number of times I've tracked down a bug or other type of malfunction where I was 100% sure of the cause since my hypothesis made so much sense, but it turned out to be wrong. It was something else.

Alternative hypothesis, for the sake of example - Someone's just really be into practical jokes. Possibly the neighbor whose alarm keeps going off, or possibly a third-party who found an easy way to trigger the alarm. But, my first thought on this thing triggering when he backs up is a rear-view sensor that uses a projection to get data. Apparently the 2018 version of his car has radar sensors that go off when backin…

I wonder if backing up would set off other people's radar detectors.

Reminds me of "Trolling for Taillights"!

http://www.cs.cmu.edu/~hgobioff/public/random_stuff/traffic

Re: Neighbor's house alarm triggers when I put my car in reverse

#212

Post by digi_owl »

DonHopkins wrote: post #209

I posted this before in the "My wife has complained that OpenOffice will never print on Tuesdays" discussion [1], but it's worth repeating: I heard a story about a terminal in a public terminal room that a user was able to consistently log in to if they were sitting down in a chair in front if the terminal, but never if they were standing up. They thought it might be static electricity, or some mechanical problem, or…

Makes me think of a story i ran into somewhere about a secretary that had sorted all the files on her office PC in different folders alphabetically.

This was back during the DOS days, and i suspect it was only discovered when she complained that it would no longer start in the morning.

It may well be that said joker had the best of intentions by sorting the keys in the numerical order...

Re: Neighbor's house alarm triggers when I put my car in reverse

#213

Post by digi_owl »

robocat wrote: post #179
SOLAR_FIELDS wrote: post #116

Earlier quoted context omitted.

I’m guessing car manufacturers have caught onto this. I drove a year 2000 car whose speakers would know I was about to receive a text/call several seconds before receiving it. I don’t think I’ve been in a model later than 2008 that’s had this problem. The noise, like the AOL dialup modem beeps, are one of those things that become cemented in your brain and immediately recall themselves as soon as you think about them…

2G GSM? https://youtu.be/jBu1ILbIKZo

Makes a guy nostalgic for beach summers when the boombox would overlay that because someone left their phone to close to it.

Re: Neighbor's house alarm triggers when I put my car in reverse

#214

Post by markwillis82 »

I currently have an issue with my iMac (also happened with the MBP) and iphone 8 (also happened with the previous iPhone 5S) that if I have bluetooth enabled on my phone and unlock it... my bluetooth mouse stops responding on the iMac. Interestingly my phone and iMac are not paired and nor is the mouse and phone.

Very frustrating

Re: Neighbor's house alarm triggers when I put my car in reverse

#215

Post by digi_owl »

mavidser wrote: post #189
beala wrote: post #75

Earlier quoted context omitted.

I can often tell that I'm about to receive a text message because my poorly shielded computer speakers will start buzzing. I assume it's caused by a transmission from my phone's radio inducing a current in the amplification circuit. I would guess this is what's happening with your GFI. Even though you're receiving the call, your phone is probably transmitting too (sending back the equivalent of an ACK or something).…

I remember old feature phones which had a fancy light on the back, which started blinking whenever a call was about to come through. Was a pretty nifty feature when you were expecting calls ['twas a time when I used to give "missed calls" for a callback].

Before UMTS came online and brought higher frequencies etc, i seem to recall novelty shops had a rack of objects one could attach to a phone. These would all light up when a call came in. There was apparently enough juice in the signal that the antenna in the object could drive a LED.

Re: Neighbor's house alarm triggers when I put my car in reverse

#216

Post by digi_owl »

geekamongus wrote: post #113

Reminds me of when my dad had strewn ham radio antennae between trees in our backyard when I was a kid. For a few days, any time he started doing his Morse code, the neighbor's garage door would start going up and down.

Makes me think of early days of wireless keyboard, where the same model would always broadcast on the same frequency.

Made for some fun times at LAN parties etc.

Even read about a pair of keyboard that managed to reach several kilometers, even though the locations had line of sight blocked by a hillside.

Re: Neighbor's house alarm triggers when I put my car in reverse

#217

Post by throwanem »

post_break wrote: post #94

When I worked at an NOC for a fairly large ISP they told me a story of an intermittent outage that occurred randomly on weekends. Something was injecting insane amounts of RF interference on the lines. They tracked it down to the node, then the neighborhood. And then finally they found the culprit. What was knocking the network out of whack? It was some guys edge trimmer. The motor in it was injecting crazy signals s…

> The motor in it was injecting crazy signals somehow.

It was too cheaply made to have an interference suppression capacitor across the supply leads, is how. Bet he got it from Harbor Freight...

Re: Neighbor's house alarm triggers when I put my car in reverse

#218

Post by rdc12 »

azernik wrote: post #127
mdip wrote: post #102

Earlier quoted context omitted.

Off topic to the discussion, but you hit on something that struck a nerve with me so I'm going to go with it . . . Oh good God, this happens to me every time one of my smoke alarm batteries starts to go. I have 6 smoke detectors and an older home where they're not all wired/battery back-up but rather all battery powered. The "chirp at 90 second interval" thing is the worst design in the universe and it bites me every…

Vaguely related - I once met a parrot that had learned to imitate that exact chirp . Maddening.

In the late 90's early 00's, we had a pet cockatiel that could perfectly mimic the sound of dial-up modem dialing. He would also do the tunes to TV theme songs and a few regular TV ads.

Re: Neighbor's house alarm triggers when I put my car in reverse

#219

Post by throwanem »

lucaspiller wrote: post #146
post_break wrote: post #94

When I worked at an NOC for a fairly large ISP they told me a story of an intermittent outage that occurred randomly on weekends. Something was injecting insane amounts of RF interference on the lines. They tracked it down to the node, then the neighborhood. And then finally they found the culprit. What was knocking the network out of whack? It was some guys edge trimmer. The motor in it was injecting crazy signals s…

On a related note it’s interesting how electric shavers (which could easily suffer from the same issue) are allowed on aircraft, but mobile devices need to be in flight mode. Are the frequencies of RF noise from an electric motor in a different range, so they don’t cause issues with aircraft?

The problem with electric motors is back EMF, not so much RF - motors don't spin that fast. (Switch-mode power supplies do switch that fast - into the hundreds of kilohertz - which is why cheaply made and thus poorly suppressed ones do tend to produce radio noise that you can hear, in harmonics at least, in the lower AM band. It'd be rare to find a tool motor that spins much over 30K RPM, and even that's on the high end.) So the noise is too low frequency to qualify as RF, but you're still dumping inductive voltage spikes into the supply, which can destabilize other equipment on the same circuit or one nearby - in this case, while the neighborhood concentrator might not have been (probably wasn't) on the very same circuit as the trimmer, it probably was on the same transformer, or else the circuits ran parallel in a conduit somewhere and the noise was getting capacitively coupled into the concentrator's supply.

This wouldn't be a problem with a battery-powered trimmer because it isn't connected to the aircraft's hotel supply - or if it is, it's through a wall wart, which will contain a transformer and at least some suppression circuitry, which will dissipate any EMF that makes it out of the tool. And in general, the way you suppress this kind of inductive noise is with capacitors and chokes, which any reputable manufacturer of a line-powered motorized tool will include in the design. But there are a lot of disreputable manufacturers out there, too.

Re: Neighbor's house alarm triggers when I put my car in reverse

#220

Post by bartread »

ptaipale wrote: post #191
chrissnell wrote: post #124

When we were kids (dating myself here), my friend had a TV with a remote control back when almost nobody had a TV with a remote. You would push the channel-change button on it and the channel knob (!!!) on the TV would mechanically turn and the channel would change. Well, apparently, the remote used an almost-audible high frequency to signal a channel change and when his dog ran through the living room, the dog's tag…

When working on plain old telephone system (POTS) multiplexers, I came up with the following story which a service engineer insisted was true: An elderly lady with several pets called the operator to say that her telephone failed to ring when her friends called; and that when it did ring, her dog usually barked first. The engineer went to investigate. He climbed a telephone pole next to the house, connected his test…

This story has been doing the rounds since at least the 1980s. I remember hearing it from a BT engineer who was visiting our school back in the day. No idea if it's true or not, but it had certainly reached UK shores as of ~30 years ago.
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