Fakin' it

For a taxi customer Finland is a very safe place. If you take official taxi the risk of being mugged or cheated with rigged meter is very close to zero. Since I deal with equipment, I concentrate on the latter case here.

A common way to cheat with a meter is a device that injects extra signal to meter, generating impression that car is moving faster/further than it really is, and thus generating higher fare.
Since Finland happens to be so safe in this context, this of course means that I haven't encountered such devices myself. I would like to however (in sense of someone sending me one for examination, not in sense of finding one installed in taxi I'm working with), since I'm really interested on how they work - and of course I would like to incorporate some kind of tech to detect these.

It's been several years since I first heard (and considered) the issue, but only about a year ago I started to get a bit more interested. Since these devices aren't exactly legal, I haven't had a change to examine them in detail (after all, knowing how they work would make defence easier), so I have to rely on information I've found from the net.

After some searching I found two class of devices: First class are connected to meter by directly cutting the wire and adding a switch that switches between normal pulse and pulse generated by an generator that continuously pretend to be driving at high speed (and thus generating high fares). There may also be signal injection involved (add new signal on top of another), but again, details are vague. Either way, since there is direct wire splicing involved, these devices could be detected even after being removed by inspecting meter wiring for irregularities.

Second ones are more interesting. Apparently (details are very thin; this is the reason why I'd love to get my hands on a few of them) they work by inductive or capacitive coupling, and they generate extra pulse on top one coming from vehicle, fooling the meter to run at higher rate (so basically similar to above, but without the need of cutting/splicing wires).

After few hours of thinking I had thought up maybe three different ways to detect both cases of tampering; in a day about 10 or so, each with both pros and cons and with varying implementation
difficulties. Some of these are variations of same ideas so I don't even try to cover them all.

When thinking of these I also realized that despite solutions should be very easy for any engineer who is worth their pay once they actually encounter the problem, someone might still try to patent them, despite of the "inventiveness" factor being near zero.

So, some cases I thought up within first hour;

If you have a GPS you can trust, you can of course compare speed reported by it against speed measured by meter. Significant difference is of course major red flag. The GPS signal doesn't have to be always on for this to work (garages or high-rise building blocking signal and so on), but if you never get signal there is a problem (antenna blocked).

GPS isn't often an option, so you'll need to analyze the signal itself. The "constant pulse generator" is of course on first glance easiest to detect. If the speed remains unchanged for too long, then there
is a generator involved. Unfortunately there is problem, and it is called "cruise control". Cruise in my car can hold the speed within 1% (yes, one percent) easily for several minutes, and for shorter periods
even at 0.1% (why yes, I do have a meter in my car that can measure speed with one tenth of km/h, designed the thing myself, Eltrip-65n to be specific). You can see how this could make a terrible false positive if triggered.

Signal timing, then. Quick changes in signal frequency - like jumping from "5 km/h" to "50km/h" within 0.1 seconds - is pretty clear red flag, and very easy to implement.

Then there is signal shape which will be altered if there are external (injected) signal overlapping the real one. Normally you expect the signal you receive to have fairly constant duty cycle, typically (but not in every car) 50%. If there is variation there, there just might be something fishy.
You'll have to be careful though, you don't want this to trigger if car for some reason really has slightly irregular duty cycle (say, sensor elements aren't placed exactly 180 degree (or 90, or whatever) difference) . So some signal processing is most likely required - I think variations of algorithms that can be used for this  counted half of ideas I eventually had, from comparing pulse  length to previous one to capturing longer sequences (tens of pulses) and analysing them then afterwards. Either way, it all boils down to fairly simple analysis of pulse periods, so I won't go further in details. I hope I made my point clear already.

And yes, this of course can apply to any case where there can be pulse signal forgery involved, not just taxis.

Pictures!

As promised, some pictures of insides of the Blu-Ray player (Samsung BD-P4600) and monitor (HP w2216).

Starting with the Blu-Ray player. From outside it is different from most players as it is kinda "UFO" shaped, for nice and easy wall mounting. Guess that (wall mounting) went mostly out of style already as you really don't see that many devices designed for such use anymore (well, TVs aside).

Taking out handful of screws from bottom of device allows the top cover to slide off to uncover the insides; on right there is "bay" that is accessible from outside for connectors. And in middle, here yet covered with metal panel are main and display boards.

Taking out metal cover and display board reveals main board. Nothing really exciting here, really. This used external power adapter so no high voltages inside. On bottom side there are two main ICs that connect to bottom metal plate with thermal tape. Only unexpected thing here was the lack of electrolytic capacitors. Apparently they weren't needed.

Like I said before, a quick check on main board didn't reveal any problems (all voltages look good, even when movie is playing and so on), so the problem must be the drive itself. Not worth the trouble as new player was only 90€.

Okay, then the display, HP w2216, from 2008. I don't remember exactly the reason why I got this specific model, best guess is that it was only 16:10 model they had available when I went to buy one.

Opening this was pretty easy, but revealed nothing really unexpected. This one has also internal speakers (black can in picture below; outside measures about 23x57mm) which I have never even tried, but I have no reason to expect them to be any good for anything.
Above the speaker there are high voltage backlight connectors.

Taking off the LCD reveals power and main boards. The LCD module has also driver board (connected to main board via flex cable; connector can be seen at bottom of main board) and entire thing was sealed with loads of conducting tape.

Power board from other side. On top there are backlight drivers, on bottom main connectors. Caps are not bulging at all and measuring voltages with just power and main board connected revealed nothing. LCD itself of course was not connected as measuring voltages when it is in place would be very difficult if not impossible. Guess I'll just put this back together and use it for some less critical stuff - maybe it'll get worse so I can locate the problem.
16:10 displays aren't exactly cheap; I got HP Compaq LA2405wg as a replacement (again, only 16:10 display they had in shop), which cost about 280€. So I can justify putting in another hour of work to get this running again. We'll see.

Everything's falling apart

I seem to be plagued by electronics breaking down right now.

First office laser printer (multifunction device; printer, scanner, copier, fax) refused to power on after a weekend. Since a printer is absolutely necessary for deliveries and invoicing, first thing I did was to call supplier. Response was what I expected, "old model, not worth repair, buy new similar unit for 400€, we can get it delivered there in two days."

So what an curious engineer is to do, but to open up the old one. And surprise surprise, I found two electrolytic caps that were bulging severely (I'd put in photos, but this was some weeks ago, before I even considered blogging, so I have no photos of that. Sorry.)
So a quick trip to local electronics parts store later I have functioning printer again, for total cost of about 50€ (parts and labor). Time well spent.

Next thing to die was home Blu-Ray player, a Samsung BD-P4600. It could play Blu-Ray disks but not DVDs or audio CDs. Because of this I suspected the laser module itself (which would be pretty much unrepairable), but I decided to open it nevertheless.

The player has external, 12 volt/3 amp power module. Because of this I expected to find several on-board regulators, each with their own electrolytic caps, and I was kinda hoping that one of them would be failing, causing the problem with disks. No such luck; I did find the regulators, but to my surprise main PCB has no electrolytics at all; it was all large chip ceramics. So back to original hunch, and since new players cost less than 100€ now, I abandoned further attempts, but only after admiring the quite beautifully systems-engineered device; everything in it was built nicely for easy assembly (and disassembly).
No photos of that either, but I still have the player somewhere, I'll try to add them later.

And now my home computer display from 2008 is dying (22" 16:10 ratio - I absolutely hate 16:9 displays). I first noticed some flicker on some shades of grey about a month ago, and by now it was getting more serious. Quick search confirmed it; most likely power source is failing. I opened it up, but both power and driver modules look healthy and voltages are stable. Damn. Guess it is time to go display shopping again. In the meantime, I think I'll put it together again and put it in less critical use, waiting it to die. Maybe I can find the real culprit then and fix it.
And third sorry here, no photos of that either, yet.

Getting started

Okay, so here I am, doing something that I never thought I'd be doing - writing a blog.

Full disclaimer first; I run a small business, Trippi oy, in Finland, with main specialization in trip meters - that is, devices that tell very accurately you how far you've driven. That doesn't sound very exciting, doesn't it? Well, there's more; friction measurement (that is, how slippery the road is - very important in icy Nordic winter for maintenance!), taximeters, accessories and so on.

Well, yes, still not exciting. Funny how it is, there are huge amount of businesses that do just one special thing that you - or I - will never even hear about. Until for some reason you need their services, only to be surprised that that small shop, the one just behind the corner with name that doesn't tell you anything actually does this. And you had never heard of them until now.

But this still hasn't explained why I'm writing this. Just bear with me a bit longer now...

Now, I am self-confessed geek. According to my father (he works with electronics too) I picked up soldering iron about the same time I stopped needing pacifier (well, there might some exaggeration there), and I if I recall correctly I've been programming since I was 10 or so. I do all the hardware and software design of devices we manufacture, and due to this I happen to follow technology news quite closely.

Which brings me to patents. The current situation (is US mainly, Europe is only slightly better) is disgusting. For small player, like me, it's a lose-lose situation. Big companies patent everything possible (there's apparently nothing "too obvious") and they are granted them with zero review. They sue and you're bankrupt. Or, if you have patent (no matter how good and valid), if you sue, they throw hordes of  lawyers on your way and you're again bankrupt. Lose-lose.

Did I mention obviousness? As an engineer, if I am given a specific problem, I often can figure out half a dozen solutions, some worse, some better. If same problem is given to ten other engineers worth their salary, they'll figure out very same solutions. This makes those solutions obvious. Yet big corporations will happily get patents for these. So it's actually lose-lose-lose.

So what can I do then? Well, this, for once. Publicly document the ideas for some random problem, no matter how obvious it seems, I happen to think of, with some solutions and dearly hope that in the long run this will ruin some litigious (sp?) lawyers' day and save my sorry behind.

In the meantime I'll just keep writing about stuff (I won't be limiting myself only to things mentioned above, there'll be other things too), which I hope someone will find interesting.