At only one location with two iPads one would go offline almost every day (but not every day) between 12pm and 1pm, for 10-20 minutes. Never the same time of day, and never the same length of time. It was always the same iPad, the other one on that network stayed online the entire time.
We replaced the iPad and the problem persisted. Finally I got fed up, put my phone on silent, ignored everything, and watched the Dropcam feed for the 2 hours near the usual time. Slowly I saw the sun light up the lockers, eventually shining on the iPad. Ten minutes later, after sitting in direct sunlight, it went offline. As the sun moved, the iPad went back in to shadow and came online on its own.
It was overheating and shutting itself off until it cooled down. The time changed because day lengths change, and the days it didn’t go offline were cloudy.
Except that the touch screen could be activated by rain. In Seattle.
There was a small cowl over the apparatus to keep regular rain off, but if there was any wind at all, it was very easy for drops to be blown onto the screen and it would start phoning apartments in the middle of the night.
Amazingly, this was among the building's least troublesome faults.
Many years ago I had an optical mouse that would act erratically in the afternoons (just wouldn't register movement). It seemed to be ok if I squeezed it while I was using it so I figured it was a connection somewhere. Eventually I realised that it was the afternoon sun streaming in through the plastic seam and somehow stopping the sensor.
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 "problem exists between keyboard and chair", but finally they noticed something else was amiss...
It turns out some joker had re-arranged the 1234567890 keys to be 0123456789, so when the user was standing up, they looked down at the keyboard and typed their password (which contained a digit, of course) by looking at the keys.
But when they were sitting down, they touch typed without looking at the keys, and got their password correct!
Report: "If my secretary logs with our account, it works. If I do, the website logs in but then later shows me errors message when I try to submit a report". Entirely repeatable. Screenshots sent showing it exactly. All of us scratching our heads. How could our web server know who was sitting in front of the keyboard?
Root cause: the username was a number with a leading zero. The login didn't care if you used zeros or not, but the internal logic did care. She logged in with them, he logged in without them (or was it the other way around?). Once logged in, the username was taken from a cookie or something that had been set at login time and fed into the internal logic, which barfed.
Lessons learned: either don't have forgiving logins, or have forgiving functionality when users use inconsistent logins.
They were indeed sharing an account with the same username and password. It was 2005 and government website, so this made sense.
But yes, I do agree with the general sentiment of "communicate via something internal, not something user-supplied".
At some point it became clear that they ignored leading zeroes during login on their end, but still included those leading zeroes when they sent it over to us, so we had a number of duplicate accounts. I purged the duplicate accounts (delete the newest, strip the leading 0s off the oldest) at the same time that they changed their code to send over the truncated number. All went perfectly, except apparently a few spouses were upset that they could no longer use their secondary account.
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...
There's a lot of options to try to isolate the problem, just thinking out loud here -
a) Back into the driveway returning from work. See if alarm goes off. Next morning, see if alarm goes off as you drive out.
b) Remove fuse for reverse assistant. (Stupid sensor thinking IR, ultrasound or RF sure-fire sign of break-in)
c) Remove fuse for reverse light. (Stupid motion detector confusing light for potential intruder)
d) Rev it up a little before shifting into reverse. (In case a resonance is the cause)
e) Roll out of the driveway in neutral. (Would be surprised if this triggered anything - if the car's movement was the cause, alarm wouldn't go off immediately upon shifting into reverse, only when it moved)
I love reading about interesting problems and creative ways to solve them. I used to wish for the same. But then I was given a super annoying one.
In my apartment I heard this beep about once every 90 seconds or so. I tried ignoring it for a while hoping it'd go away. And just so at the right frequency and infrequent enough Impossible to determine direction. But also just loud enough to be annoying after hours and hours. I spent several hours trying to pinpoint it. Including putting my head up agaisnt numerous neighbors doors to see if it was coming thru the walls.
I ended up downloading a dozen different audio apps for phone. And found only one that gave out an accurate enough histogram of dB volume level. Most weren't good enough. I needed to differentiate between 2 and most were sensitive enough of reading. I was able to triangulate the direction thru several patient iterations.
Turns out it was coming thru the wall.
Be careful what you wish for. Because you might end up with something arbitrarily dumb and annoying!
I was renting in a century-old house that had been converted into apartments. Every night, around midnight, this very high-pitched hum would start, and continue until almost dawn. None of the other residents ever heard it when they were around. While the exact timing varied, the time during which it happened overlapped with my sleep schedule (I was working a late tech support shift at the time) and it kept me awake. Earplugs didn't really seem to help.
There didn't seem to be any obvious source. I did exhaustive work to try and track it down - even got the permission of the owner and my fellow tenants to try shutting off the power at the breaker box in the middle of the night to see if that helped. (It didn't.)
It wasn't always constant, but it was around enough and preventing me from sleeping enough that I was going slowly insane. I had my ears checked for tinnitus - nope, I had and still have darn good hearing. I started reading about the Taos hum, looking into resonant frequencies, and finally stumbled across the answer.
The noise started a little while after everyone in the building went to bed. It stopped shortly after they got up in the morning. It was the sound of the century-old plumbing system at full pressure. If I just left a tap open a trickle, and the noise went away along with my sleep-deprivation.
20 years ago, in my first graduate job, we were issued pagers. One day my friend lost his - and it was on silent mode. We really didn't want to tell the company that it had disappeared.
Then we remembered that, at a certain time - I recall it being reasonably late at night - the device would emit a single, short, beep. I don't remember why, but even on silent mode, that beep would sound.
At five minutes to the hour - because this thing's clock wasn't synchronised, and we didn't know how accurate it was - we all positioned ourselves around the house. Silent as a mouse we waited, until - yes! - there it is, somewhere upstairs.
Now that we knew that it was actually in the house, it was just a matter of finding the thing. It was in his pants pocket - but they way they were folded in the wardrobe, the pocket wasn't where you'd expect it to be if you did a casual "pat the pockets" to see if it was in there.
Eventually a spark of inspiration hit me, and I reached up and pulled the cord on the window blinds behind the computer desk. I found myself nose to beak (through glass) with a startled mockingbird. "Beep?" it said, and flew off.
Eventually I decided to move out, for other reasons. My last act after everything was out of the place was to buy a cheap battery powered alarm clock, sat on a high shelf in a bedroom closet in a hard to see spot, programmed to go off at 2am every night for 5 minutes.
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 time. If I didn't know any better -- since there is no clock device and these things are not networked in any way -- I'd swear they are also programmed to only start chirping between the hours of 2:00 AM and 4:00 AM. I've lived here 10 years. I have never had one of these fail in the morning, middle of the day or afternoon; only in the middle of the night. Hunting down the one of the six devices that is failing with its way-too-infrequent chirp that's so high-pitched, only a dog could figure out where it's coming from, is made extra fun when you're in the fantastic mood that being awoken from a pleasant dream in the middle of the night and have the joy of hunting it down in your boxers in a cold house.
How much more complicated would it have been to also include a visual indicator. The things have an LED on them that continues to blink as the battery dies. Why not also have it either stop blinking (to conserve battery) or blink faster -- anything to make it easier to identify which of the infernal, identical, devices is in need of a 9-volt.
Thankfully, they're due for replacement this year. Now I have to research which of the models that are available handle this circumstance with a little more intelligence (that don't cost a hundred bucks a pop). This is such an easy-to-solve problem -- I don't want a "smart smoke detector", I want a $25 one that A) detects smoke and B) reports when it needs other attention in a way that is useful. Heck, I'd pay an extra $10 for the latter feature even knowing it would cost them no more than the "dumb chirp" method.
There was a very bad house fire a few miles from me about a year ago and the person who lived there died in their sleep while the fire raged. The rumor was that the home had a bunch of smoke detectors without batteries in it and it was spread through our neighborhood as a "cautionary tale". I'm willing to bet there's a story of being woken up in the middle of the night for a battery change chirp in there somewhere.
(You can troll people into thinking you have magical powers, rub the batteries of a just-failing calculator/scale/wristwatch in your hands and you'll get another ten minutes of use out of them)
You can get a smoke alarm with 10 year battery life to reduce the likelihood of this happening. When all are purchased in one batch, you can then pretty much replace them all at once -- if first battery goes, next ones are soon to follow.
I got some unconventional looking ones from Jalo Helsinki  for my house. They work well and look good. However, I know some people working at Jalo, so my opinion is biased. There are several other long battery-life smoke alarms on the market from different manufacturers to choose from.
If I'd had a baseball bat or wooden sword, I'd have smashed that thing free like a piñata!
That said, everyone should check their alarms at least once. You should be able to find appropriate "testers" to purchase with alarms. I use CO alarms at the place I live in (gas-heated water), and each of them I tested with what I affectionately call "carbon monoxide in a spray can".
This in fact is a very popular around the world electronic kit for beginner hobbyists, because it's trivial to build and has only few components. I remember it from electronics magazines in Poland.
Next day, enraged, we tried again. Eventually we found it in the bathroom trash can.
The designer apparently thought that emitting a single beep every five minutes or so would be an awesome low battery indicator.
I didn't know what kind of thing was making the beep, naturally, which was unhelpful.
It took about a month of me slowly going mad before I finally found the thing at the back of a desk drawer.
My solution is to just change all the batteries at once so i dont have to guess (and if you guess wrong you then you wont sleep tomorrow because of the beeping)
I wish there was some visual indicator to tell which one was faulty.
I bought half a dozen of them to install in our new house years ago, thinking the nightly find-the-beeping-^+=¥€ games were finally a thing of the past.
When one started beeping, I did the rounds, figuring I'd be back in bed in minutes. Well, I wasn't. Turned out the fool-proof indication was to have the normally green LED flash red instead.
Did I mention that I am colour blind?
I had this happen a few months ago except it wasn't a low battery alarm. It kept yelling "FIRE FIRE" but then turning off. Of course FirstAlert apparently doesn't indicate which alarm is causing it. They say the initiating one flashes a different pattern but I didn't find one. Ended up, after getting no sleep at all, replacing all 9 of them with nests. At least then if one fails I'll know which one.
Manufacturers can get away with it because even if they screw up, an angry customer doesn't really affect their sales in any meaningful way.
A few years ago I used "Find my iPhone" to chase down my phone in the house, buried under some pile or another. Unfortunately I had earlier been using AirPlay to play music through remote speakers, so of course the emergency tone played through the speakers, not the device.
I had high suspicion that it was that. But not hearing it thru neighbors door. And with how loud it was and the fact I could hear it thru my front door and not theirs. Made the hunt for it so much harder.
If you can't get an alarm to shut-off or stop beeping, no matter what you try, then give serious thought to the possibility that there's a second alarm nearby which is the source of the noise.
After 3 goddamn hours of searching, and having run to the store to buy 9-volts and replaced every goddamn battery in the house, we found a carbon monoxide alarm thrown INSIDE the return air duct of the HVAC unit...
To my ears it always sounded the same volume. And to some apps. It wasn't considered loud enough to be read in a meaningful way.
I was a noobie computer programmer in my first job. After being there for a few months my mouse started to have issues. It stuttered and refused to move correctly.
So I'd take the little grey ball out and clean it and it'd be OK again. But the next day it'd do it again.
So I ended up with the cleanest fucking mouse on planet earth. Yet every so often it'd stop working... on parts of the screen. Other parts it'd work. I ended up using the keyboard a lot.
The mouse would work fine all day some days. Some days it would work fine until about 2PM then it may or may not work.
Eventually I figured out that when the sun shone through the window it created a beam across my mouse mat. When the mouse was moved into the beam it would stop working. So I took it to bits and discovered that the ball would roll a little disc, that disc had little holes in it, there was also an LED and a photodetector. So the mouse was counting the blips in light to determine the movement in the mouse. I guess the cheap plastic was allowing the bright sunlight to bleed through the case causing the photodetctor to go bonkers.
A secondary thing about that cheap as shit PC was you could hear the video card render the screen. It'd buzz when the screen was mostly blue, when it was white it would be silent.
Of course opening a mouse up and not breaking it is quite hard, they're made to break and be replaced. Current bugbear is Logitech keyboard stand pieces that appear only to be there to break and thus require keyboard replacement - again it seems a design with a penny's more of plastic would be almost invincible.
site:reddit.com/r/talesfromtechsupport printer stopped working skylight
Even worse than that I had already saved the post when I read it the first time.
Ubuntu doesn't print to Brother printers on Tuesdays.
Moved the VGA away from the RCA, no buzz now.
Talking to my father in the morning, he indicated that his neighbor had taken up Ham radio and he was having to put filters on various devices to reduce interference. To this day, I wonder if his spotty wifi in the house is related to his neighbor turning his system...
I knew someone who lived two blocks from a radio station, and they would get interference everywhere, there would be staticky top 40 music coming from the phones, from clock radios, from the stereo. It would come and go. They would complain, the radio station would fix something, but in a few months it would be back.
He was probably onto something.
Listening to the tranmission using the arc the tower generates to ground!
For your list, and I’d do a) and not bother with b) and c) as a) eliminates them well enough (point the emitters away from the alarm sensors). For d), I’d put a light cloth in the tailpipe, enough that it will change the exhaust note across RPM range, but the car will still run. Your suggestion leaves the slight possibility of a false positive if we accidentally hit the resonant rpm range. For experimentation only, don’t drive to work a banana in your tailpipe.
One last one: throw it in reverse near the house, but not in your driveway. Could be some weird parabolic blah blah acoustic thing focus thumpy exhaust waves at the house sensors.
I suppose there’s the possibility that a 2.4Ghz radio transmitter of some sort could be responsible, but this way out there and would be way down in my list. SDR and a dongle would be handy here.
> What does your neighbor think of this lmao
> > I don't have time to stay around because I tend to lag for work and have to leave as soon as I do get to my car.
How ... convenient.
I bought an electricity usage monitor plug and started to measure every electricity consuming stuff, but couldn't account for more than 3 or 4 daily kWH. Then I went in vacation for one week, turning off almost everything in the house, and the electricity consumption, that I can check every day, had barely moved. Something was consuming at least 20kWH every day in my home and I didn't know what it was.
At the same time in prevision of the winter, I bought a thermal IR camera to spot isolation problems. I started to play around with it, and discovered a fairly large hot spot in the bathroom, on the bottom of the bathtub. Touching it with the hand, it sure felt warmer than you would expect from a baththub. Maybe it was some hot water? But the water heater was on gas and my gas bill was fairly normal. The hotspot would also not go away after hours. Then I remember a visiting friend remarking weeks ago that my bathroom was warmer than the rest of the appartment.
To test my suspicions, I tried to play with the electricity meter of the appartment. After some experiments, I found out a switch that would turn off the mysterious heat source. The baththub started to cool down and the power usage displayed went down to 0. My theory was validated! Something under my bathroom was drawing around 800W constantly every hour of the day and every day of the week and that was making my appartment so hot in summer and my bill so large.
At this point, the only thing I could do was contacting my landlord and detailing my findings. It turned out he had installed a dehumidifer in the basement the year before to dry out the air and fight a moisture problem, but he had configured it to a very low setting, like 30% humidity and that was making it work constantly. The dehumidifer was installed just below my bathtub and its operation was heating it at the same time. Since it was an old home he had bought out a few years before, he didn't know where the basement was drawing its electricity from. Well now he does.
He reimbursed me the electricity and changed the settings of the machine and then my electricity consumption went to almost nothing... until november came and the cold of the last weeks of fall started to hit Montreal, but that's another story.
That way they can see debug output of what happens when he hits reverse.
[as someone else already said]
Weird EM interference from electronics, ultrasonic backup sensors, Magic Stuff Related To Reverse #1.
> Alternatively, if the alarm did go off, this ex-mechanic would be at a loss as to how a car with no powered systems could do that.
Maybe it was caused by Magic Stuff Related To Reverse #2, or maybe it turns out the system is actually powered when you thought it isn't.
Looking over your other comments in this thread, I feel like you're approaching the topic from a position of someone who's an expert in cars and electronics, and thus has almost everything important in their memory already. But in cases when one isn't an expert with a thing one's debugging, I'd err on the side of doing the tests that seem ridiculous, at least if they're cheap to do. Discovering that it's probably Magic Stuff Related To Reverse #1 is a fair result, and should then be followed by reading up on what else gets activated/actuated when one's car gets switched to reverse.
From what I heard this is not uncommon.
Because me being a sysadmin for the past 14 years would go directly to the logs and see my client timing out.
You could actually just press that "off" button at any time, and the dog would look around and do that funny "Dog shrug" thing they do, and go upstairs and lie down, even if it was the middle of the day. We had, essentially, a remote controlled dog.
I vividly remember when I realized it. One day in class we were watching a tape and the TV was whining the entire time. After the tape was over, the teacher started talking about what we'd seen, but didn't turn the TV off. I asked him to, because the sound was so annoying. A bunch of kids started saying they didn't hear anything, which made me think I was crazy until one other kid stuck up for me and said she heard it too.
In television sets, this high frequency is about 15 kilohertz (15.625 kHz for PAL, 15.734 kHz for NTSC), and vibrations from the transformer core caused by magnetostriction can often be heard as a high-pitched whine. 
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 set, and rang the line to subscriber's house. The phone didn't ring, but the dog barked loudly. He tried again, now the phone rang.
Climbing down from the pole, the engineer found:
- This was in a country where the ringing was done from one of the wires against ground (not across the pair) (I think it was England).
- A dog was tied to the telephone system's ground post via an iron chain and collar.
- The ground post was in dry, poorly conducting ground.
- The dog was receiving >50 V of ringing voltage when the phone rang.
- With this torturous treatment, the dog would start barking and urinating on the ground.
- The wet ground now completed the circuit and the phone would ring.
OK, this story has a definite "urban legend" ring to it. Mythbusters wouldn't have tested it with a real dog, I guess.
I had built myself a simple modem for packet radio (ham radio; very slow modem for use on shortwave bands), and wanted to test it. However, I was at home, and at the time I used either the HF station I had installed at my office in the university or the one at the radio club down the hill.
Heck, I'd only try some local comms, anyway. I got an old transmitter out of a cabinet and strung up a dipole antenna under the ceiling in the living room. I tied one end to the curtain rack either end of the room, called the radio club, agreed on a frequency, and off I went.
When I keyed the transmitter, I could hear a commotion starting upstairs. It died down, and I didn't think more of it. After a while, new commotion.
Next day, I met the occupant of the apartment above at the mailboxes; she said her cat had acted up last night - running around the living room like it had the devil on its back.
Turned out it had a metal collar, and loved to snooze on the floor right under the window, as the radiator on the wall below the window made it real warm and cozy there.
When I keyed the transmitter, I basically had a very high RF voltage at the end of the antenna - and the cat, whose collar was a mere few centimeters away, got enough of a current induced in it for the cat to go ballistic. Poor thing.
It would be easy enough to test without involving a dog. They've done plenty of electric-shock myths with ballistic gel dummies.
I thought it was pretty cool that she could sit on her chair and change the channel & volume without getting up.
I suspect that if a dog had been involved that cable would have quickly become a tangled mess! (I'm not sure how common "wired remotes" were, that was certainly the only one I ever saw, in the early eighties.)
It was basically a rubber squeeze pump (just like on a blood pressure machine) and a rubber tube connected to the tv. When you squeezed the pump, the pressure in the tube would click the dial forward one notch.
 Was this exact one: https://i.ebayimg.com/images/g/kyIAAOSwz71ZPcLZ/s-l300.jpg
 Looked something like this, IIRC: http://1.bp.blogspot.com/-O2PtM-x0fDc/UyFjySzfuCI/AAAAAAAAJ9...
What does this mean?
Understandably, the complaints got louder and angrier as no one on our engineering or prerelease teams were able to reproduce it, but easily half the bug reports were all about this issue and identical. After 2 weeks of trying every configuration of video card, OS, and any other alchemical recipe we could think of, my partner on the test team stumbled upon the license crack online while searching for anyone else having this problem but not having reported it to us directly.
As a brief respite from this ongoing madness, he decided to install the crack on a clean machine and aee how it worked so we could report it. Lo and behold, the problem reproduced on the first try. This whole time, indignant, angry users who were actively threatening our team and vowing to never use another product from our company had been bested by a poorly written crack.
Before exposing the secret, I asked dozens of the most vocal and vicious reporters to please email me a particular log file, and give me contact information where we might get in touch with them as we were close to cracking the case. (Pun intended, and this was before we had very clear rules around personally identifiable information, but even with the policy at the time, these weren’t our customers so I felt less anguish about it.). I received all of it and more, invited them to share their experiences on the forum threads, and then tactfully but clearly explained exactly why they’d seen this problem. I offered to work one on one with anyone who felt my accusation was in error, but not one single affected user replied or followed up after that message.
This was before validating license keys over the internet was really possible so a lot of people just used our application with a key from a public cracking site. Of course, we also knew about this list of cracked keys and our application would pretend to accept them. But if you actually tried to use the application, it would appear to be doing something for several minutes but fail with a mysterious error inviting the user to submit a log file to support.
Of course, the log file was secretly marked to indicate that it had come from a pirated copy and the customer would get a polite call from the sales team.
It worked out pretty well, a lot of customers didn't know they were using pirated software (or so they claimed; somewhat plausible given the nature of the utility) and were happy to pay and the sales team got a lot of solid leads. Evil vanquished, good prevailed, and I got paid.
We had a problem with piracy for awhile. We spent nearly a million dollars on some of the best licensing software out there and over 2 years of tweaking it to try and eliminate all attack vectors and we still had piracy. We learned even the best anti-piracy methods will be broken eventually. In the end, the proper solution was pretty simple... we just rewrote our application as a web app and now only people who pay can login.
I mean come on people, if you're using professional software and expect to be paid for your work, pay the other professionals for their work too.
If I may be permitted a brief comment, I recall several years ago a situation where we received complaints that our rather computationally-intensive software was running on some people's laptops without them having installed it, rapidly draining their batteries and heating the machines up, and what did we think we were playing at hijacking their systems?
It turned out that the culprit was a modified version of our software for a distributed computing project that would apply the credit generated to one particular account, presumably belonging to the user who had distributed the cracked version. IIRC (though I may be mistaken) they were distributing it bundled with some other cracked Windows software.
> My S2000 car alarm would be set off whenever I microwaved blueberries. Some experimentation revealed it was anything with excess water. Buying a new microwave solved the issue but I don't like thinking about how poorly shielded the old microwave was. I tried moving the for further from the kitchen or keeping the keys far away to no avail.
As for the S2000, I guess water coincidentally changes the frequency of the leaked radio waves to match the car alarm?
The company being as cheap as it was, I simply began using the microwave as a deliberate noise source for testing the device's operation under adverse conditions, placing a few mugs of water in the microwave for a few minutes, and deliberately setting my channel to collide with the microwave.
Or frozen blueberries, but why would anyone buy frozen blueberries.
Because they are available and inexpensive year-round, and they defrost well and are good in many applications. Outside of the peak of local season, its the best way to buy blueberries.
Because 'fresh' blueberries out of seasons cost 3 times as much and taste like nothing much.
Eventually I tracked it down to microwave usage. Whenever the microwave was in use, I lost WiFi.
And the story doesn't have that big a payoff to justify that either.
All the plugging did was make me slightly annoyed and averse towards the brand and that bloody catchphrase.
It was too cheaply made to have an interference suppression capacitor across the supply leads, is how. Bet he got it from Harbor Freight...
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.
I had something like this happen once that was interesting. We had recently got a Simple Human automatic soap dispenser and had it sitting in the kitchen by the sink. I was bored and started playing with a small RC helicopter and kept hearing a weird noise but didn't know where it was coming from.
For whatever reason, every time I would throttle up on the controller it would trigger the the dispenser to dispense soap as if someone had stuck their hand under the sensor. I ended up finding a large puddle of soap in the sink and then it clicked as to what the noise was.
I have a 2016 WRX with what should be the same exhaust. When you start the car, it starts with a high 2000-2200RPM idle and drops from there. If it needs to warm up, it will sit around ~1800rpm which is exactly where the stock exhaust makes the loudest drone.
So simply starting the car and letting it idle should result in it hitting all the revs that trying to reverse would (unless OP is awful at driving stick and way overrevving it here).
I find it way more likely there's a sensor interference issue than it's an exhaust issue based on the other information. My second guess would be some IR from the halogen running lights / fog lights / other lights in the car interfering with a motion sensor.
It turned out that an iPhone receiving a phone call tripped it -- even before it starts to ring! Making a phone call didn't do anything. Here's a 13-second video:
I'd love to hear comments about the possible cause.
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). The current induced causes a difference between hot and neutral and the GFI trips. It's surprising that it can induce a strong enough current! I'm not sure what wattage cell phone radios operate at.
Edit: Ah missed the detail about outgoing calls not causing it. That is very strange! Perhaps a cell phone engineer can shed some light on that!
RFID works by the same principle, incidentally - in this case, the energizing signal comes
from a primary winding in the reader housing, and the secondary in the card powers a little CMOS chip that in cheaper models just modulates the voltage drop over the winding to return a constant code, and in more expensive models receives a challenge nonce signaled by the card reader and modulates the winding to return an encrypted response. It's a really interesting application, and an impressive but often overlooked early example of "IoT" style smarts done well.
GFCI works by detecting the difference in the current flowing between the hot wire and the neutral wire. It needs to work very fast (to avoid the human touching the wire getting electrocuted) so any slight difference in current would trip it off. The current induce by your phone's speaker probably causes enough difference in the current to trip it off.
You can run an experiment by turning off your phone's speaker for incoming call. See if the speaker is the culprit.
In that case too, sending calls didn't trigger the interference, and neither did picking up the received call.
It may well be that the control channel's initial "wakeup" transmission is done at a very high power to ensure the phone receives it clearly, and then after some back and forth the two adjust their power levels and move to a different channel for the actual call.
We live in a crazy world.
Without knowing the details of the alarm system it is hard to have an educated guess.
Source: I wrote firmware for microwave/PIR motion detectors for a few years.
Rear cross detection and blind-spot detection is an option package.
This allows my car (2016 WRX Limited) to warn me about cars flying by when I am backing up out of a parking spot for example.
I’m willing to be the guy/gal next door has those broken window alarm strips installed, one part of the strip is loose and when the cars RPM drops as the clutch is let out while in reverse it slightly vibrates the window causing the contact to short (or break) and thus the house alarm goes off.
Good fun :)
Skip to 18:50 and listen on for couple minutes.
Love the caller complaining about his brother in law.
> Maybe you neighbor is setting off his alarm on purpose just to mess with you haha!
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.
The WiFi on my girlfriend's laptop would fail when an HDMI cable was plugged into the laptop. Changing the channel on the router "fixed" it but we never could figure out the ultimate cause.
I can pause my Roku box using the Kodi remote app on my phone. This occurred when I inadvertently used the wrong remote to pause the Roku. It appears only to work if the Raspberry Pi running Kodi has gone into some sort of standby mode, possibly making the Kodi remote app send a wake signal which is interpreted by Roku as the pause signal.
Seem to recall reading about similar issues related to WIFI and USB3.
As for the remote app stuff, i guess it's time to break out the packet sniffer.
Or it could be that one of the alarm inputs is in high impedance, but then it should trigger to way more than just putting a car in reverse. Little bit of site surveying with portable spectrum analyzer may reveal something. Or playing around with wide-band emitters -- which may be illegal.
Then again -- it may be something else. Good hint would be to know what sensor is triggered exactly. Usually alarm control panels tell that.
View this YouTube video to get a good idea of how the car sounded (my brother's was a bit louder): https://youtu.be/cNWv5WpamPc
I assumed it was interference from some sort of PIR motion detector transmitting a signal to say it saw some motion, but I suppose it could conceivably have been caused by the car going into reverse.
I never debugged it, I just threw the doorbell away and bought another.
If his garage is angled, he could try neutralling out to the street before starting the car.
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.
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 backing up (https://www.subaru.com/engineering/safety.html):
> Rear Cross-Traffic Alert uses radar sensors to help warn you of traffic approaching from the side as you are backing up, utilizing an audible warning and flashing visual indicators in your side mirrors and Rear-Vision Camera display
Reminds me of "Trolling for Taillights"!