Cheap Cell-Phone Detector

An anonymous reader contributes a link to a BBC News article on a cheap cell-phone detector created by six New Zealand high-school students for a business competition, excerpting "The detector, which they have called CellTrac-r, works by picking up the bursts of radio frequency activity that emit from a mobile each time it sends or receives a call or a text message. The device can detect these bursts of electro-magnetic energy up to a radius of 30 metres. It can also measure the amount of the energy to determine the distance of the mobile.", and noting "Seems like a perfect /.er hack project, and as initiator I get 5% of gross profits."

Comments

Neat, Now if only

[novalogic]

... I can tie it into a cellphone JAMMER on my car, so I can detect moron drivers on phones as they come close, and jam them when they become a danger.

I can see police cars equipted with this kinda stuff in places where Yack and Drive is illegal.

These kids are rich.

Re:Neat, Now if only

[sr180]

Great, so they look at their phone to work out why it dropped out right as they swerve their vehicle into you..

Re:Neat, Now if only

[Osty]

... I can tie it into a cellphone JAMMER on my car, so I can detect moron drivers on phones as they come close, and jam them when they become a danger.

Because the previously inattentive driver wasn't enough a danger, now you have a confused and angered driver more concerned with why his cell phone stopped working than paying attention to the road?

Re:Neat, Now if only

[double_plus_ungod]

they can't swerve their vehicle if their boxen are infected with virii thus allowing the detection unit to transmit spam, even through the reverse firewall.

Re:Neat, Now if only

[Anonymous Coward]

virii and boxen eh?

The only phrase flamebait you forgot was 'begs the question'.

Re:Neat, Now if only

[bruthasj]

We wouldn't want you to be the car that rubbernecks the scene of a heinous car wreck where people are trying to dial 911, possibly working through procedures to save a person's life.

Re:Neat, Now if only

[ComaVN]

These kids are rich

I haven't RTFA, but unless the have patented this thing, I doubt they are going to profit from it.

Come on, you can detect cellphone activity with *ANY* loudspeaker. It cannot be hard for any electronics company to design such a device from scratch and start producing them in bulk within two months.

Re:Neat, Now if only

[Anonymous Coward]

Nop. The time between bursts can be up to 2 hours (in Holland). Enough time to go past the detector undetected. What they need to do is be a base station, have a 6dB stronger signal than the current basestation so the phone will connect to it, deny the connection (the phone will go back to its previous basestation) and you have evoked an active response from the phone (that can be detected).

Re:Neat, Now if only

[Albanach]

I can see police cars equipted with this kinda stuff in places where Yack and Drive is illegal.

I don't drive, though I'm often a passenger in cars. I'm often a passenger on buses too, strange as this may sound to some North Americans. In both situations I'll frequently use my mobile phone - are the police really going to start tracking vehicles and trying to establish if there's more than one occupant? What about single occupant cars with a proper hands free kit installed? What about sensible folk who when driving ignore the fact their phone was ringing and let it divert to voicemail? I really can't see the police wasting much time with this.

Re:Neat, Now if only

[ElvenMonkey]

Great, so they look at their phone to work out why it dropped out right as they swerve their vehicle into you.

Then imagine how the driver tries to explain to the police / their insurance company just why they were swerving..

I'd love to take a mobile jammer with me on trains and other forms of public transport, or into cinemas / concert halls, upon hearing "I can't talk long, I'm on the train", or even the phone ring, I'd love to be able to press a button and jam their conversation, especially as most are conducted at about 40db. The only thing that stops me is that it would jam medical pagers for doctors and emergency service reserves on duty..

Re:Neat, Now if only

[__aafkqj3628]

With a large enough noise generator (power-wise) and antenna, you could cover a nice big area - who needs to say it's legal. (see this)

Also, this device these kids are touting is nothing new. A google search will reveal various circuits schematics for cell phone detectors.

Re:Neat, Now if only

[tzanger]

The only thing that stops me is that it would jam medical pagers for doctors and emergency service reserves on duty..

That, and I'd personally beat you senseless for determining that you have any say whatsoever over my use of a cell phone on a train, bus or any other form of public transit. I am perfectly capable of using my cellphone properly; your use of vigilante justice would earn you some in return.

Re:Neat, Now if only

[beakerMeep]

they might also try this at hospitals where they ask you to turn off your phone so that you dont interfere with x-rays and pacemakers.

Re:Neat, Now if only

[YrWrstNtmr]

What about single occupant cars with a proper hands free kit installed?

No such thing.
It's not the hands that are the problem, it's the brain.

Re:Neat, Now if only

[Anonymous Coward]

I live in Japan where probably close to 90% of the population has a cell phone... it is illegal (read discouraged) to use a cell phone on any form of public transportation or as a passenger (including busses, trains, cars, and bicycles)... So that's kind of a non-issue here... (although in the same breath, law isn't enforced in Japan unless you cause damage)

Re:Neat, Now if only

[afidel]

Ah, so we are going to outlaw any conversation in a vehicle? What about children, I know mine can be quite distracting. And how about eating, drinking, applying makeup, etc. The fact is we should REALLY be working on having cars drive themselves because it's something people do VERY poorly statistically. We didn't evolve to pilot a vehicle moving at 60+mpg, we evolved to stalk prey on grasslands, quite different sets of requirements. Just because drivers on cellphones are the pet peeve of the year doesn't mean we should outlaw it, we should fix the root of the problem which is people driving in general.

Re:Neat, Now if only

[afidel]

Yeah, putting out high power jamming signals is going to be SO much better for that delicate medical equipment then the tens to hundreds of milliwatts that a cellphone puts out *cough*

Re:Neat, Now if only

[Anonymous Custard]

"We didn't evolve to pilot a vehicle moving at 60+mpg, we evolved to stalk prey on grasslands, quite different sets of requirements."

What planet are you living on? We did evolve to drive 60 mph machines. Look: we've evolved, and we drive cars. Simple as that. Did we evolve to live in houses? To use computers to find unimaginibly large prime numbers? Did our fingers evolve to type on keyboards so that we might communicate on /.?

Just because certain people are lousy at it doesnt mean that it's a problem for our entire species.

Re:Neat, Now if only

[beakerMeep]

I was under the impression this was detection equipment not jamming. But yeah nice attitude you got there.

Re:Neat, Now if only

[afidel]

Did you read the comment you were responding to? He specifically talks about jamming....

Re:Neat, Now if only

[tomhudson]

I'd love to be able to press a button and jam their conversation, especially as most are conducted at about 40db.

Bzzzt! Wrong answer :-) A normal conversation is 60 decibels. 40 decibels is 1/100 of that. http://science.howstuffworks.com/question124.htm p.It might be annoying if you were sitting right next to them, but not to the people a couple of seats away.

Re:Neat, Now if only

[beakerMeep]

Ah...I meant the equipment in the article but i can see how my post could be misread. I meant the post as an alternative GOOD use for dection equipment rather than his jamming idea.

Re:Neat, Now if only

[Cpt_Kirks]

Does anybody know of a simple design for a cell jammer?

Every day I want to jam idiots who commit DWT. If some asshat is sitting still at a green light, you can make book that his/her head is cocked to the left...

A 150-300 foot circle of silence around my car would be perfect.

Re:Neat, Now if only

[Cpt_Kirks]

What about children, I know mine can be quite distracting.

That's why cars have trunks.

Re:Neat, Now if only

[BroccoliGod]

The only thing that stops me is that it would jam medical pagers for doctors and emergency service reserves on duty..

That, and I'd personally beat you senseless for determining that you have any say whatsoever over my use of a cell phone on a train, bus or any other form of public transit. I am perfectly capable of using my cellphone properly; your use of vigilante justice would earn you some in return.

To paraphrase Ennio Flaiano: "On Slashdot there are two kinds of cell phone fascists: fascists and anti-fascists."

-BroccoliGod

Re:Neat, Now if only

[Cpt_Kirks]

Oooh, thank you.

Now I need to go home and heat up my soldering iron.

Re:Neat, Now if only

[Anonymous Coward]

It's not ANY conversation that's the problem, it's phone conversations in particular.

If you pay close attention to your in-person conversations you'll notice that people have a sort of flow control built into body language. So if you're talking to your passenger and suddenly need to pay attention to the road, you can shut up and stop listening, no problem.

On the phone, all this flow control is disabled, and people have a strong instinct to keep the flow of conversation moving. So a situation that SHOULD be granted extra brain attention is often deferred because, for instance, there's no way to delay your turn to speak, or no way to signal that you are no longer listening, and the other side isn't really aware of your situation at all.

It's actually possible for the brain to manage itself and its scheduling fairly well and give low priority to the cell conversation, but this is not what people do. It'd be a pain to try to talk to someone who was doing that anyway, since they'd randomly stop speaking or listening in the middle of a sentence.

Re:Neat, Now if only

[gcaseye6677]

I can see police cars equipted with this kinda stuff in places where Yack and Drive is illegal.

This type of law enforcement, like speed limit enforcement, will be primarily for the purpose of revenue generation. Cell phones in vehicles are not the problem, inattentive drivers are. And it doesn't matter what the source of the distraction is. Besides, what if the passenger is using a phone? No politician would suggest that passengers and drivers both cannot use cell phones in a vehicle.

Re:Neat, Now if only

[tomhudson]

The original poster said 40 decibels. That's a LOT lower than normal speech, which is 65 decibels.

Read the post, read my answer, become enlightened.

Re:Neat, Now if only

[Tony Hoyle]

If your children distract you and you have an accident that's illegal and will probably result in a ban.

Eating, drinking, applying makeup is already actionable as you're not in control of the car when doing those things (up to a max. 2 years in jail if you cause an accident)

Round here the morons that talk on mobiles are already in deep trouble with the law.

Re:Neat, Now if only

[Anonymous Coward]

You get 60+ MPG?! Must be one of them hybrids.

Ok, on a serious note, yes, the problem is driving in general. But the solution, a well designed and run public transportation system, is considered by too many to be a waste of time and money.

Of course the auto and fuel industries are one of the reasons why it's considered a waste of time and money, but that's another story.

Re:Neat, Now if only

[Anonymous Coward]

. . . and I'd personally beat you senseless for . . .
another Internet Tough Guy.

I've got the US model from www.globalgadgetuk.com, and needless to say, I'll use it whenever I want in a movie theater, restaurant, or other appropriate location where I spend money on the entertainment/environment.

Some people need to have their decisions made for them. It appears as if you might be one of those types as well.

You must think that you are pretty important to threaten violence to protect your cell phone usage.

I'm sure that your mom won't panic when she can't get in touch with you every half hour.

Re:Neat, Now if only

[alienw]

It's not a LOT quieter, it's only 30% quieter. Human hearing is logarithmic, that's why the decibel scale is logarithmic.

Re:Neat, Now if only

[alienw]

Just because you are a bad driver doesn't mean everyone else is. Good drivers can drive for decades without a single accident. It's just that it's too easy to get a driver's license in the US.

Re:Neat, Now if only

[tomhudson]

In terms of power, it is 1/100th. In terms of perception, it's still less than a normal conversation.

The original poster was complaining about people talking on cell phones at 40db, which is a lot less than 65db, so the original poster had gotten it wrong. Now if he had said 90db, I'd have kept my yap shut :-)

Re:Neat, Now if only

[Anonymous Coward]

You could only beat me if you caught me. Since I'd only be using proper tradecraft, that would be rather difficult. Another note, ever wonder why your radar detector goes off when there are no police around, just consider us 'vigilantes' as looking out for you and yanking your chain at the same time. I just wish I could get that Tesla Coil to shutdown cars {Of course only those traveling very slowly ;>}
Moral To Be Learned==> Don't court disaster and
Disaster won't court you!

Re:Neat, Now if only

[utexaspunk]

any car with OnStar basically has a cellphone built into it. how will you know it's not just OnStar?

Re:Neat, Now if only

[Amorpheus_MMS]

I've got the US model from www.globalgadgetuk.com, and needless to say, I'll use it whenever I want in a movie theater, restaurant, or other appropriate location where I spend money on the entertainment/environment.

It says right on that site: "If you have a problem with mobile phone usage in your establishment and want to eliminate it, then look no further!" Why don't you let the owner of the establishment decide if customers may use their phones or not? It's not your call who gets to do what in somebody else's house. You're free not to spend money if you deem the service unsatisfactory.

If jammers ever get popular here, I could use a cell phone jammer detector. There's got to be something illegal about vigilante jamming.

Re:Neat, Now if only

[Anonymous Coward]

I'll use it whenever I want in a movie theater, restaurant, or other appropriate location where I spend money on the entertainment/environment.

Hmm, funny how the parent of your post did not mention any of those places. Sounds like you have some built up anger and wanted to vent on someone who uses their cell phone properly.

Re:Neat, Now if only

[Anonymous Coward]

Assuming you are in the US, then I beleive it is illegal.

Re:Neat, Now if only

[Rei]

That, and the fact that it's illegal, for precisely that reason...

Re:Neat, Now if only

[Rei]

Cell phones are incredibly easy to detect, and if they're unencrypted, are incredibly easy to listen in on (although you usually only hear one side of the conversation at a time unless you tune into the tower side ;) ).

I used to work on a project dealing with a system that looked at the electromagnetic spectrum. Just do an FFT scan in the 800's of Mhz (I forget the precise ranges off the top of my head); the cell phone signals and tower signals pop up like little invitation flags. They're blatantly obvious in the spectrum. With our software, you could just click on any signal, tell it the proper modulation, and listen if you so chose. And the software wasn't anything that complex, really.

FFT scans are great for dealing with cell phones, because they get you your data quickly, and you don't need incredible precision. They work by taking raw data in from the radio (instead of having the signal preprocessed for a single frequency like most radios output) into an A/D card, and then doing an FFT on the digital data to get, say, 1k worth of signals computed at the same time. You have the radio then tune in large increments, and can iterate over the spectrum's area of interest in no time. It's good for catching burst transmissions and frequency hoppers, too.

Re:Neat, Now if only

[NanoGator]

"... I can tie it into a cellphone JAMMER on my car, so I can detect moron drivers on phones as they come close, and jam them when they become a danger."

Are you going to jam their music system so they don't fiddle with the controls? How about jamming people eating while driving? If not, you're not improving your safety all that much. You've basically accomplished being an asshole with the side-benefit of jamming the phone conversations of people nearby who are not your intended target. (i.e. pedestrians.)

"I can see police cars equipted with this kinda stuff in places where Yack and Drive is illegal."

Jamming is illegal, and you can't jam one phone specifically.

Re:Neat, Now if only

[Dibblah]

Yeah. Only if you don't have a proper mobile phone network. .

Re:Neat, Now if only

[Rei]

All I can say is, it worked fine in Cedar Rapids two years ago ;)

Re:Neat, Now if only

[Anonymous Coward]

"Does anybody know of a simple design for a cell jammer?"

A two-by-four.

Re:Neat, Now if only

[Anonymous Coward]

bzzzt! Wrong answer. I think you failed to read the post you are replying to. You are actually agreeing with the poster's point.

Re:Neat, Now if only

[gunnnnslinger]

Diddo good sir! I agree. Why is it so annoying that someone is talking on a cell phone in a public place at the same volume that other people are speaking. If I'm on/in a bus/subway/restaurant/club/store, and I'm talking on a phone at the same volume as everyone else, what makes what I'm doing so annoying? Some people just like to hop on the bandwagon and complain about the gripe du-jour, whether it be cell-phones, SUV's, George Bush, pop-music, etc... It's life, live it. Get on with it. Ill talk to whoever/whenever/however . It's different if it's outside of politeness, and in a place you wouldn't even talk without a cell phone. For instance, a funeral, wedding ceremony, movie,etc... But Im just tired of people who have a chip on their shoulder out of the box for someone talking on a cell phone.

Re:Neat, Now if only

[dgatwood]

No kidding. Here's what I don't get. Technology like this could be used for really good purposes. Like out in Utah right now where that woman is missing in the woods. Odds are, she probably carries a cell phone, but there aren't any towers within range to triangulate where she is.

But instead of trying to think of constructive uses, all the Slashdot crowd has come up with are hundreds of pages saying the same rambling crap about how they'd like to use it to jam phones in movie theaters. I can do that now with a 12v battery, two pieces of wire and a metal file. Hell, I can do that by walking over to the person, ripping the phone out of his/her hands, throwing it on the ground, and stepping on it. Much more effective, as not only does it stop the conversation, it also will reinforce the notion in that person's head that his/her behavior was socially unacceptable.

How about coming up with useful ways to use this technology? Anyone? Anyone

Re:Neat, Now if only

[stephanruby]

And chances are, this cell-phone tracker can probably track your jammer, so be careful with it.

Re:Neat, Now if only

[severoon]

Most people talk a bit to a lot louder on the cell phone than they would if their conversation partner were right next to them. Most people don't *want* others to hear their conversations, and as it happens, most people don't want to hear others' conversations either.

This is a problem that can be solved by technology. Cell phones ought to have a quiet-talk mode that allows one to speak very, very softly yet be clearly and loudly heard on the other end. Of course, it would also have to employ some kind of limiting technology so that sounds do not exceed a certain maximum.

Well, technology? Do your thing!

sev

Re:Neat, Now if only

[severoon]

I can't believe you've pushed this one up to the next level. All right, then...I guess I have no choice. I'm going to my garage to start working on a cell phone detector detector and a cell phone jammer detector detector. But please, people, no mas! This is getting out of control!

sev

Re:Neat, Now if only

[sycotic]

all it does is detect the cellphone...

I'm not sure about you but there is a law coming in in our country (New Zealand) where sure "Yak and Drive" is illegal in the sense that you cannot be holding a telephone, there is no reason why you could not use handsfree however (seeing as the whole problem is that people usually only have two hands and you need two of them for driving).

Re:Neat, Now if only

[Anonymous Coward]

40 db? That's not loud! If you meant 40 db above ambient noise, making it 75-95db, then that would make sense.

Re:Neat, Now if only

[Bad_Feeling]

I have always wondered about that. Everyone today has a "digital" cellphone, that supposedly sends everything up in digital packets, so how come so many people with scanners can still tune into converstations?

Re:Neat, Now if only

[evilempireinc]

Actually a lot of stuff can set of radar detectors on the K and Ka bands w/o being one of you people. Just read any radar detector review and look for the part where they review how many false alarms they got.

Re:Neat, Now if only

[Anonymous Coward]

Maybe you would prefer a new device I am working on. It samples a cell phone conversation and then mimics either of the voices so you can 'spice' up the talk a bit:

Girl: How are you honey?
Mimic: What do you care you fat pig!
Girl: What!???
Guy: Hey, I didn't say that!

Re:Neat, Now if only

[Piquan]

You assume that the OP was using the 0 dB reference point of 0.0002ubar. Remember that dB are relative: he was actually saying 40 dB, relative to the ambient noise in the restaurant.

Re:Neat, Now if only

[tomhudson]

No, that's not what the poster said.

I'd love to be able to press a button and jam their conversation, especially as most are conducted at about 40db. The only thing that stops me is that it would jam medical pagers for doctors and emergency service reserves on duty..

"especially as most are conducted at about 40db".

40db over ambient noise in a crowded restaurant would be loader than a jackhammer, and on a par with standing next to a jet taking off.

Re:Neat, Now if only

[__aafkqj3628]

Why wait?

Re:Neat, Now if only

[Eternauta3k]

How about a sponge bath? (dilbert)

Re:Neat, Now if only

[Anonymous Coward]

I've paid money for a cenima ticket, and you, you arrogant selfish cunt, want to inflict your shitty rigtones and moronic conversation on me?

I'll see your vigilante justice and raise your phone up your arse, but you'd probably enjoy it, faggot.

Re:Neat, Now if only

[Hognoxious]

Most people talk a bit to a lot louder on the cell phone than they would if their conversation partner were right next to them.

They only have to do that if it's a long-distance call.

Cheap Cell Phone detector?

[Flerg]

Why would you want to detect cheap cell phones?

Re:Cheap Cell Phone detector?

[sotonboy]

A surprisingly accurate answer to this question is available online. Just click on the link to the article, and READ IT.

Re:Cheap Cell Phone detector?

[boogy nightmare]

Look at the parent post again and READ IT. :P

Re:Cheap Cell Phone detector?

[Anonymous Coward]

Look at the parent post again and READ IT. :P

Read? Come on now, you know thats asking alot of the average /. reader.

Re:Cheap Cell Phone detector?

[Anonymous Coward]

the title of the post is "Cheap Cell-Phone Dectector"...the parent comment is making fun of the wording...you know...it detects cheap cell phones...its supposed to be funny :D

Re:Cheap Cell Phone detector?

[Anonymous Coward]

No silly, it's a "Cheap Cell" "Phone Detector". You know, a phone detector that runs on cheap AA cells.

Sheesh, *read* the durn thing.

Re:Cheap Cell Phone detector?

[Gordonjcp]

To save time when you're mugging people for their phone.

Re:Cheap Cell Phone detector?

[nz_geekcore]

lol, i can't believe some people are too blunt to get this!!!!

Re:Cheap Cell Phone detector?

[Anonymous Coward]

Say you're a cell phone salesperson . . .

Re:Cheap Cell Phone detector?

[puckett_jw]

LMAO, thanks for getting my day started with a laugh!

Re:Cheap Cell Phone detector?

[Demanche]

I was actually thinking the same thing....

"I wonder if my samsung would get detected by this...I always knew it was a piece of crap"

Then I actually read the article.. huge dissapointment on my part :/

Tracking down specific people

[robolemon]

Seems to me like you could use this to trace someone down by text messaging them repeatedly and tracking them down. Coupled with using something like Yahoo! Mobile to send the messages, this seems like it could cause some definite privacy concerns.

Re:Tracking down specific people

[novalogic]

I would doubt that. First of all, you'd have to do an awful lot of needless "Ping'ing", and if the person knew there was a danger, simply turn the phone off.

And ofcourse, you need to beable to send this kinda stuff, I've seen it reported that IM services keep limited logs of IP's that use that.

Besides, if your gonna stalk someone, and be within 30 meters, AND have an active connection to Yahoo, you'd beable to use better ways to locate the person then a radio ping which may or may not work based on how crowded the area is.

just dosn't seem like a good method based on the way it works.

Re:Tracking down specific people

[Pius II.]

There are so-called "quiet" SMS that the police use for tracking cell phone users. These are SMS without text payload which "ping" the mobile phone without ever showing up on the display.
Of course, their tracking method goes a bit different: they triangulate the distance from the towers. Since every cell phone tower consists of an array of antennas, you can simply measure on which antenna the signal is strongest for an approximate direction. Combined with the distance measurement (from signal strength), this gives quite a nice accuracy (~100m). Of course, that would be of no use on large events, but it's enough to track, say, a software patent violator in the woods.

Note that here (in Germany) you officially need a judges permit to actually use this technique, but since these messages are basically invisible, their use without permit is to be strongly suspected. Here is an article (in German) dealing with this topic.

Re:Tracking down specific people

[Anonymous Coward]

if you have access to node information, the cell company already knows where you are in order to send messages to you.

signals are emitted every so often, in order to keep track of you as you move out of range and into the range of another cell (tower, not phone).

the idea of 'pinging' using sms, is daft, unless you had access to that phones engineering screen and also a list of the node addresses. either that or access to the cell network.

Re:Tracking down specific people

[mgv]

Since every cell phone tower consists of an array of antennas, you can simply measure on which antenna the signal is strongest for an approximate direction. Combined with the distance measurement (from signal strength), this gives quite a nice accuracy (~100m).

Except that signal strength is dynamically altered by GSM and all other advanced mobiles - you don't want the mobile transmitting at full strength all the time, just the minimum amount to get through reliably because:

1. Your battery life will be pitiful if max power is used
2. You will "Jam" one frequency/timeslice over the whole radius of your transmission.

The big advance of GSM over Analog phones (similar with CDMA I believe) is that they could work well with high basestation densities, and they do this by keeping the power down, not up.

So signal strength does not tell you how far away the phone is.

Michael

Re:Tracking down specific people

[ScrewMaster]

I don't know anything about cell phone protocols, but if phones send some sort of indication of current power level the tower could still make some kind of estimate. In fact, given all the hoopla about this technology, I wouldn't be surprised to find that cell phones do apprise the tower of their power output.

Re:Tracking down specific people

[dave420]

If you were within 30m of them to begin with. If you think that's a privacy concern, you need help. I mean, you can hear someone's ringtone further than that - are they privacy concerns too??

Re:Tracking down specific people

[multipartmixed]

This whole "signal strength" strength is a boat load of red herrings.

I don't know how the tracking software works per se, but you can bet your backside that it probably employs:

1. Which cell [antenna cluster] you're logged into
2. Which sector of the cell you're using (around here, there's usually three, and they are directonal)
3. What the TDMA transmit delay is

3 is a little less obvious -- GSM uses TDMA to divvy up the channel. The phone and the tower need to know how far apart they are, for speed-of-light reasons -- this is why cellular switches are all run off atomic clocks.

Since we know the time for the signal to reach the phone, we know how far away it is. We also know the direction (down to 120 degrees).

Finally, GSM phones keep tabs on up to six nearby towers, and the GSM network must know which ones the phones can see in order to do tower handoff.

So, now we have a several approximate vectors and distances. It shouldn't be hard to come up with their intersections. I think it can be done with two angles and two distance measurements.

Re:Tracking down specific people

[Jason Hood]

seems like it could cause some definite privacy concerns.


Well the target is using a device that broadcasts a signal on common frequencies. If you are using a device that broadcasts a signal, there can be no privacy concerns relative to emission. Thats like telling the other team the exact play with _no_ encryption before the snap and getting pissed when they acknowledge it. If you are that nuts about privacy, dont talk or type and stay home.

oh no, not another list!

[lanswitch]

as initiator I get 5% of gross profits

1. post cheap hack on slashdot.
2. ???
3. Profit!!!

Re:oh no, not another list!

[Caedar]

Oh no, not another overused joke!

Already have one

[shird]

I already have one, its a set of speakers on my desktop. Everytime a cellphone gets a call/text i get a:

dicky-dick-dicky-dick-dicky-diiiiiick

Also useful for knowing when Im about to get a call and can start looking for my phone well in advance before it starts ringing.

Re:Already have one

[Anonymous Coward]

What brand phone/service do you have?

Re:Already have one

[jlanthripp]

That happens to me too, though I'd use a different word to describe the sound. I don't get a dick every time I get a phone call...still have the one I was born with :-P

Also interferes with the home stereo, the television, etc. - pretty much anything that involves an audio amplifier and speakers. And it does it every now and then, maybe every 5-10 minutes, call or no call.

This is with Cingular, on GSM. And the service sucks too, dead zones all over the place. Fuck GSM, give me back my CDMA!

Re:Already have one

[Chep]

*ANY* GSM will do that to poorly insulated speakers, especially if there happens to be a bit of cable with the magic wrong length just before the audio amplifier. f'r instance, I had to cut the cables of the speaker for a radio alarm clock I have in my bedroom (I use it only to project the time on the ceiling, I'm using a proper audio device for waking up purposes). The thing was detecting my cell phone 7 or 10 meters away (which pretty much means anywhere in the flat, plus the neighbour's phone at times).

Crappy old CRTs (or crappy obsolete VGA cables) will also give you some funky video too. El-cheapo car radios are also especially prone to this too.

Re:Already have one

[Lord Kano]

And from under your desk eminates the sounds

ducky-suck-sucky-suck-ducky-suuuuuuuuuuuuuck

LK

Re:Already have one

[mge]

The GSM phones do this over our desk phones

Re:Already have one

[Chep]

fuck Cingular, then. I have zero coverage problems with Orange or Vodafone. And Bouygues' extended coverage GSM+ is reported to rule.

Oh, wait.

Re:Already have one

[nkh]

The sound is more like a tu tu-lu, tu tu-lu but it was not my problem: I never had this kind of sound without a call. I would be freaked out if my cell phone was calling home like yours every 10 minutes. Of course it could be explained by your dead zones with the phone trying to amplify its signal, thus producing the magical music.

Re:Already have one

[Artega VH]

I was going to suggest my monitor.. you get little fuzzy horizontal lines at random places... The benefit here is that it only does this when i'm about to get a call or an sms rather than when its just loggin onto the cell..

Re:Already have one

[Anonymous Coward]

Everytime a cellphone gets a call/text i get a:

dicky-dick-dicky-dick-dicky-diiiiiick

i dont know what kind of people call you...but i never get phone calls about dicks.

Re:Already have one

[minus9]

"dicky-dick-dicky-dick-dicky-diiiiiick"

How many dicks is that?

Re:Already have one

[Anonymous Coward]

How many dicks is that?

a lot.

Re:Already have one

[Anonymous Coward]

The cellphone transmits a beacon to let the network know which cell it is in. If you get a call, then the network first tries to contact the mobile only via the cell in which it was last seen. If it doesn't reply, then the call setup is broadcast to all cells, which is obviously an expensive action. Thus the network tries to minimize the number of times a phone is not reachable in the cell in which it is expected to be when a call arrives. The network can set the beacon (location update) frequency. Some networks set it as high as once every 10 minutes, other networks set it as low as once every two hours.

The mobile unit will tell the network when and where it goes online or offline or switches cells, but it is possible that this information is lost (no coverage, network overload, drained battery). Otherwise unnecessary location updates are scheduled to mitigate the loss of location information.

Re:Already have one

[Anonymous Coward]

that sounds like fun new variation on duck duck goose... dicky dick dicky dick dicky diiiiiiiiick! you're it, come with me. I'll be back in a bit for the rest of you.

Re:Already have one

[josh crawley]

I already have one, its a set of speakers on my desktop. Everytime a cellphone gets a call/text i get a:

dicky-dick-dicky-dick-dicky-diiiiiick

Well that's life as a gay prostitute for ya...

Re:Already have one

[Anonymous Coward]

you're lucky it's only your speakers, when my phone is next to my monitor, the [monitor] starts shimmering like crazy before [the phone] rings.
scared the jeebus outta me when it happened. at least it helped explain the occasional flicker in the monitor (cellphone pinging the tower).

Re:Already have one

[Anonymous Coward]

HALGHLAGHLAHGLAGHALGH

(Site text probably NSFW)

Re:Already have one

[Anonymous Coward]

And this is exactly why cell phones and their users' attitudes really piss me off!

Imagine, I'm riding on the train, minding my own business, listening to (or at least trying to listen to) some nice soothing music.

But NOOOO!, I can't because every couple of minutes, the music is interrupted by somebody's frigging cell phone spewing EMF into my headphones.

Used to be that my discman was good for something, but no more thanks to fuckers that have to be in touch with whoever all the time, and to hell with everyone else.

And this is all before the phone rings or the phone luser even starts talking!

Re:Already have one

[fcolari]

Thirty-seven!?

Re:Already have one

[Anonymous Coward]

Easy, just wrap your headphones in tinfoil!

Re:Already have one

[Anonymous Coward]

You are most likely very near a cell tower/antenna.

If you're within a couple hundred feet of the antenna it will bleed through on all sorts of devices.

Re:Already have one

[Anonymous Coward]

Wrong movie... you're thinking "Clerks" with the "thirty-seven" but the "how many dicks is that" question is from "Resivour Dogs."

Re:Already have one

[Craig Davison]

Dick from your speakers?

Maybe you Thought you could replace SSL/SSH with something much better you designed this morning over coffee.
Alternatively, maybe you thought Hey, skins, what a cool idea.

Re:Already have one

[JTek]

You must have a Nextel

Re:Already have one

[Clubber Lang]

37

Re:Already have one

[rjstanford]

I take advantage of this - like many others, my car has a small storage bin directly below the radio. I drop my celphone in there while I'm driving. The interference, while at a fixed volume, will disrupt my music sufficiently to detect an incoming call even if I would otherwise miss the ringer. Of course, it also serves to detect things like long bridges, so its not perfect. I can tune it out (while still checking to see if its lit up), but it annoys my passengers sometimes.

Re:Already have one

[kevquinn]

Real phones also pick up that kind of interference - you can hear the mobile of the person on the other end of a phone line (perhaps in a different country) before it rings. Spooky for the other person if they don't realise what the diddly-dit-dit-dit noise is and you tell them their mobile is about to ring :)

Over Christmas a friend gave me a cheap tacky little reindeer hat thingy that you stick on top of anything nearby. The reindeer nose (led) lights red whenever there's significant radio activity from nearby mobiles. Sold as a cheap piece of Christmas fun that light up when _your_ mobile phone rings, of course it actually lights when any nearby phone rings, sends or receives an sms, etc.

Another friend has a similar circuit built into his car air freshener, which similarly flashes whenever there's mobile phone activity nearby.

Incidentally, I'm not sure measuring distance would be all that accurate, just based on signal strength. The latter depends on the power of the mobile phone's transmissions, which depend on how good a signal the phone gets from the base station...

Finally!

[WegianWarrior]

...a great way to find my cellphone those times when I put it on silent ringing and then forgets where I put it down :) (don't laught - it happens more often than I like to admidt). Now, if they could also find a way to indicate not just how far away the mobile phone is, but also in what direction... shouldn't be hard - either a directionloop, or two antennas 90 degress apart.

Re:Finally!

[geminidomino]

How do you get 2 antennas 90 degrees apart? Wouldn't you need THREE points?

Re:Finally!

[Lord Kano]

Once I dropped my cellphone into a 2 foot snow drift. I had to keep calling it and sifting through the piles of snow in my driveway. That sucked ass.

LK

Re:Finally!

[antic]

"don't laught"? I admidt that I don't even know what laught is! Maybe I forgots?

Re:Finally!

[jigyasubalak]

Mobile can still be found by calling to it thru the land line...ok, ok...almost everyone has a landline and mobile. I'd appreciate this in a keychain more.

Re:Finally!

[Patrik_AKA_RedX]

Right. And what makes you think you'll be able to find your cell phone tracker when you lose your phone? I bet when you buy one of these you'll end up finding both the tracker as the cell phone on the bottom of the laundry bin after a 4 hour search.

Re:Finally!

[trentblase]

That's why you need my new, patented, cell phone tracker tracker.

From the same people who brought you the Trace Buster Buster Buster

Re:Finally!

[Anonymous Coward]

Mobile Phone Sniffer?

You'll find a schematic already available from the Elektor Electronics web site:
http://www.elektor-electronics.co.uk/minipr oj/deta ils/010128.htm

rb

Re:Finally!

[rk]

I used to do this until I forgot where I put my cell phone detector.

I can't wait for these kids to put out a cell-phone detector-detector.

Got it already

[darnok]

So this thing can detect a mobile phone only when it sends or receives a call or text message? I'm not that smart, but I figure that would tend to coincide with either the phone making a ringing or beeping noise, or someone talking into it.

Hmm, how could I possibly detect this using attachments I've had on my head since birth ...?

Re:Got it already

[supersandra]

Sure, you have a point of some kind. However, this device could much better be used to detect cell phone use when people have a reason to conceal it. As a student I know that plenty of cheating via text messages and camera phone images goes on, as do the authors of the article. It even mentions that they're going to try out the devices at the boys' university during exams.

RTF post/article, you silly person... :)

Re:Got it already

[darnok]

It still only tells you when something is happening, and an (approximate) distance from the detector where it's occurring. How will this help to detect cheating during exams, where there are potentially 100s of students within a 30m radius? Sure, they'll know a phone is being used, but who's using it? Is the plan to stop the exam and have everyone turn out their pockets?

I haven't taken exams for many years, but I know several people that rely on mobile phones for critical reasons (e.g. being in touch for health reasons, contact with kids on public transport, etc.) that would make them reluctant to give them up for the duration of a typical exam. How is this issue currently handled in academic environments?

Re:Got it already

[sotonboy]

1>. Sending text message. No sound created.
2>. Phones are constantly talking to the nearest base station. Even when youre not actively talking down it, a signal is being emitted.
3>. Silent (ringer turned off) calls.

Re:Got it already

[wisdom_brewing]

currently, in the uk at least, there is a zero tolerance on mobile phones during exams, you hand in the phone at the start of an exam, and collect it at the end, it is asked that you do not bring the phone at all into the examination rooms, and if youre found with one you instantly get 0 for the exam you are taking (as with all cheating) even if it is switched off... as ive already said, if you HAVE to have a mobile phone on you, you switch it off and hand it to the invigilator...

Re:Got it already

[trendyhendy]

As someone who goes to said University (Uni of Canterbury) I can say that cellphones are allowed in an exam, but you must turn them off and leave them in your bag at the front of the room. Though that doesn't mean that everyone remembers to do this; the result is some LOUD polyphonic ringtone going off in the middle of the exam.

Re:Got it already

[Airw0lf]

I haven't taken exams for many years, but I know several people that rely on mobile phones for critical reasons (e.g. being in touch for health reasons, contact with kids on public transport, etc.) that would make them reluctant to give them up for the duration of a typical exam. How is this issue currently handled in academic environments I am currently at university, and for the last couple of years, there has been a massive "crackdown" on cellphones in exams. If a phone is found on you at any point in the exam you will be escorted out and have to face a disciplinary hearing - which will probably end up in you being expelled for cheating. This applies even if your phone is turned off. I'm fairly sure you'd even get in trouble for having a phone with no battery :) Our exam procedure requires that bags be placed at the front of the room. If you have a phone in there and it rings, the bag will be taken out, and the owner will have to go to the exam centre to claim it. Upon claiming the bag, "appropriate action" will be taken against you by the chief examiner. So in this environment, I do not see any room for ANY cellphone usage at all, no matter how good the reasons for it. This is my university, YMMV.

Re:Got it already

[markxz]

t still only tells you when something is happening, and an (approximate) distance from the detector where it's occurring

It would be possible to walk the aisle (as invigilators often do when they get board) with the detector set to pick up strong signals.

There are very few situations where somebody would need to have a mobile phone turned on in an exam, the institute hosting the exam will have a contact number that could be used in case of an external emergancy. If a candidate became ill the invigilator would need to be notified and the institutes phone could be used.

Re:Got it already

[Anonymous Coward]

You overlooked that there is another use for vibrators, too.

Re:Got it already

[ermannob]

2>. Phones are constantly talking to the nearest base station. Even when youre not actively talking down it, a signal is being emitted.

Well, not really constantly... GSM cell phones ping the base station every 60mins. So at least every 60 minutes there's network activity. But if you move away from one base station, then the phone will have to register itself in another base station, making the activity interval potentially shorter.

reliability

[dncsky1530]

If it can pick up cell phones in a 30 metres radius, one would have to think that in a conjested area, it may pick up many cellphones and possibly confuse the system. Also I would like to know if this device could interfere with peoples mobile calls, if so, cell phone jammers (this one isnt pocket sized) are already avaialable.

Re:reliability

[sotonboy]

I dont think theyre trying to detect phones in a congested area. But I may be wrong because I acutually read the article. Its for use in Exam halls etc.

And as I understand it it, its a DETECTOR, not a jammer. Again though, I got this be READING THE ARTICLE, so I may be wrong.
Just to save you going to the troube of reading it yourself, it points out that detectors are also available, but are prohibitively expensive, this is a cheap version.

It Figures

[tonyr60]

Christchurch is the technology centre of New Zealand, and Tait is the largest technology exporter

Re:It Figures

[builderbob_nz]

I wouldn't go to the extent as saying that Tait was the largest tech exporter from NZ (OK its a given for hardware, but what about software?) but I think that it's great that they are encouraging kids to be creative and have fun learning about new things (heck, they probably now know more about my own cell phone than I do).

My hat comes of for Tait, and I challenge all those slashdotters in decision making positions to get the kids off the streets and get them involved.

And finally (sorry all those in Aussie, but I can't resist) woo-hoo another Kiwi first!

Re:It Figures

[sammcj2000]

yay go christchurch!!!!!!! im a Opawa / St.Martins man myself!

Re:It Figures

[AtomicBomb]

As another Kiwi, I sometimes think we should get over the "Number 8 wire" mentality* if we really want to develop our high tech industry. A clever trick may have helped us to get over the difficult times in the past, or brought a decent living for the few founders of various tech companies.

But, we cannot create an industrial base from just ingenuity. It involves a lot of teamwork, planning and support. These are boring and difficult work. The spectacular success of the semiconductor industry in Taiwan and Telecommunication gear in Scandinavian countries in the last two decades are admired by many. But, there is no coincident: both value education very high. The university graduate level in New Zealand, esp in tech area, is not exactly high in OECD. And, many NZ employers in the tech industry today still consider ME/MSc as over-qualified... We got to ask ourselves, "are we prepared?" before cheering upon every minor success. (For the guys behind the detector project, good on you, keep your good work going.)

*For non New Zealander /.er, "Number 8 wire" refers to kiwi ingenuity. It is the spirit to solve problem on hand with minimal resources using some clever tricks. I can say Bruce Simpson (the DIY cruise missile guy is a prime modern day example). While all these ideas are cool, they cannot carry us very far. These are not breakthroughs, but cool imitations....

This is news?

[Captain_Chaos]

Come on! We've been getting these for free with our Coke and popcorn for years. I've a small green Heineken bottle that lights up when my cell phone is active, and also a pen with a little red light at the end which does the same.

There's even ones that don't need batteries and work solely on the energy that's broadcast by the phone (although these have to be attached to the phone so they're not much good as "cell phone detectors"). All of these have been around for quite a while (or at least they have here in Europe).

Re:This is news?

[Anonymous Coward]

In Europe? That's nothing. They're really abundant... in Japan!

*ducks*

Re:This is news?

[tfb]

This isn't the point of these things. As lots of people have pointed out, It's pretty easy to detect a phone at short range, as anyone with any kind of small-signal audio system (microphone amplifier, probably even line-level things or higher) can tell you. In fact the first phone I had used to make my (CRT in those days) screen flicker when it was close enough.

But that's not what these things are for. There are plenty of environments where you are *not* meant to have mobiles turned on because: inside planes or in hospitals (both places where there is critically important small-signal electronics), in exams (no electronics, but pervasive cheating by text message), and in many other places. For those environments you want something which will detect a phone at significant range, and you *can't* assume that you can hear someone or the phone ringing: someone trying to cheat in an exam won't have the phone set to ring, and won't be talking into it.

Of course, you can get detectors already, but they're significantly expensive - hundreds of pounds. And you need plenty of them, too. Think about an exam: one for the room itself, one for each toilet, and probably at least one more for the corridors between the room and toilets. 4 or 5, minimum, or several thousand pounds. How many exam rooms does a school use at once? Maybe 5? So they might need 15-20 of these things. Not a small amount of money for a school. Similar things are true for hospitals and so on.

Reducing the cost by a factor of 10 or more, as these people have done, is a *major* advance. So yes, this is news.

Re:This is news?

[Captain_Chaos]

I still don't think it's a big deal. Those gadgets I was talking about that I have, they light up when I'm 10 m away, and they cost next to nothing. It can't be that difficult to make them work at 30 m and even if that increased their cost a hundredfold, they would still be cheap.

Re:This is news?

[Anonymous Coward]

Bollocks... the revolutionary component is.... an amplifier!!!!?? c'mon!!! wowie!! a major advancement.... man, you need your head re-examined.

Mobile detector pen

[worf_mo]

I remember that a couple of years ago you could get a sort of pen that would light up whenever somebody within a certain range (a couple meters) was using his cell phone. The CellTrac-r described in the article sounds like a similar gadget, with possible extra capabilities (like determining the distance).

Re:Mobile detector pen

[milenko11]

It's the same idea as all of those keypads for the phones that light up 19 different colors. You can make the lights go off by using any cell phone near the phone with the lights.

Re:Mobile detector pen

[jamiefaye]

From watching Cops too much, it seems that most undercover operations involve a radio link between the operative(s) and the support team. I always wondered why the dealers and hookers don't have some sort of RF emission detector as a countermeasure.

Of course, the presence of cell phones, particularly those which are pinging the tower, throws this idea off a little - too many false positives.

Perhaps a two color indicator - one for "RF in the neighborhood" and the other "RF classified as from a mobile cell phone". Cell phone pings would blink both.

Re:Mobile detector pen

[electricfox_hosting]

Actually, they are still available on eBay.

I'm in a club at UC Berkeley called Berkeley Innovation. For one of our projects, we attempted to come up with a solution that would reduce the number of switched-on phones entering a lecture hall (to reduce disturbance).

At first we tried to build our own like these kids, until we ran across the cell phone pen. It's sitting right here on my desk, and it works. We even purchased a tried and true cell phone detector that is is very similar to the one they describe (same 30m range), and it even can emit a tone (not just lights). Not trying to put down these students for their efforts (or for the judges, who might rethink their definition of originality), but a little google action would have yielded these devices. Or for that matter, the suckers would bought some of the first prototypes for $1,000! We bought ours for $20. Hmm, maybe I could fund the trip to New Zealand I've always wanted to take by bringing a few of these little gems with me to sell for a 50x profit...

your distance will be wrong

[pbjones]

mobile power output varies and is controled by the phone, you can't derive distant by looking at power output.

Re:your distance will be wrong

[J Isaksson]

True, but it's still very useful for triangulating the phone with multiple sensors.

Its easy

[FraggedSquid]

Just listen for somebody shouting "I'M ON THE TRAIN!". As if we didn't know already.

Re:Its easy

[horza]

It's put quite well one of those moments too?

Phillip.

Isn't it Obvious Anyway?

[mauthbaux]

In my personal experience (living on a college campus) It seems that people with cell phones are plenty willing to show them off and use them (nearly constantly).
So what then, is the practical use of such a device? From the description it sounds like it would only detect a phone as it is receiving or sending a message anyway. Someone sending a message would be obvious enough anyway. When recieving a message, they seem to make pointlessly loud and obnoxious noises already. Pardon the skepticism, but I can't see much practical use for such a device (other than the obvious geek factor).

Now if you could integrate something similar into handheld console games, that would be a little more interesting. Imagine not only being able to play play the games against others, but getting a signal when someone around you has the same game and is willing to play agaisnt you.

Just my uninformed two cents

Re:Isn't it Obvious Anyway?

[stupid_is]

I think that at least one use of them was mentioned in the article (but of course, who reads that, nowadays?) in that students use them on silent mode during exams. Schools aren't necessarily the richest institutions in the world either.

Coming soon to a movie theater near you

[Lord Kano]

so that the MPAA goon squads can kick your out and confiscate your phone before you can text all of your friends and warn them not to waste their money of whatever shitty movie you had the misfortune of seeing first.

LK

Re:Coming soon to a movie theater near you

[ragnar]

I would hope the cinema operators would eject anyone who would be so insensitive as to do text messaging during a movie.

Re:Coming soon to a movie theater near you

[Lord Kano]

My phone has a "silent" option, how about yours?

As long as they're being quiet, I don't care what they're doing.

LK

Re:Coming soon to a movie theater near you

[AtomicBomb]

Cell phone detector has already been around... Whether cinema, university, prison etc decide to use it is another matter... It is cool to see young students designing those thing. But, the product is around for a while and it is
not really that expensive (click the third photo, the price is about 150 UK pound, about $270). Already quite affordable for the institute who want to install them...

The industrial guy who is mentoring the students exaggerates the price of rival product a bit (he said it is at least 350 UK pound), and ignored some cost. For example, to support the secondary student, the local university/ govt dept may not be hesitated to pay some cash to buy a bare board. To make a customer product, you need to have a decent case. Just the plastic mould can be a few thousand dollars... And, a real company need to pay their engineers. We all know we are not that cheap. My guess is they have not lowered the unit cost revolutionally. It is more like hobbyist vs commercial product...

It sounds cool to catch the students who cheat in the exam... But, in practice, it won't work esp in university. (Prison is another story)... Say, you are running an exam in a big lecture hall. Can you make sure there is no valid user around. The univeristy visitor may have one, the gardener mowing the lawn outside may have one, the courier may have one. Every single outsider walks near the lecture hall will signal a false alarm....

Re:Coming soon to a movie theater near you

[AtomicBomb]

Oops the link does not show up in the last post.
Here is the link to the $270 cell phone detector

Re:Coming soon to a movie theater near you

[ragnar]

The light from the cell phone is annoying. If someone can't spend 2 hours not communicating with other people to enjoy a movie, the person shouldn't go. Also, regarding the "silent" option, the problem is that the person's voice answering the damn phone isn't silent.

Re:Coming soon to a movie theater near you

[Lord Kano]

Also, regarding the "silent" option, the problem is that the person's voice answering the damn phone isn't silent.

Um, we were talking about sending text messages. You don't need to use your voice for that.

LK

The MPAA will be using technology like this soon.

[GrpA]

Just think about it.

Give it 4 or 5 years, and mobile phones on new generation networks will have high resolution image stabilised digital cameras and the ability to transmit this image in real time, already compressed, down multi-megabit networks.

Such a phone would video a movie from a pocket, and there would be no evidence, because it would be transmitted away.

So there is a huge value in these detectors...

Just remember to leave your mobile at home when you visit the cinemas, or having it ring during the movie will only be the start of having a very very bad day...

GrpA

Simple explanation on directionfinding by radio

[WegianWarrior]

I often make the mistake of assuming people know what I know... in this cause, how most modern ADF (Automatic Direction Finding) equipment work in aircraft... Mea culpa =)

A coiled antenna - also know as a directionloop - recives the signal strongest when the 'open end' of the coil points towards the transmitter. If you have two coiled antennas, one orientated dead ahead (in relation to you) and the other pointing left-right (ie: being 90 degrees apart), it is reasonable easy to use the difference in signal strenght to figure out the direction the source of the radiotransmitter - in this case the mobile phone.

Three points (or antennas) would be needed if you want a fix on the radiotransmitter (mobile phone) and not just the direction.

Re:Simple explanation on directionfinding by radio

[geminidomino]

Heck, I was just thinking Geometry. I was picturing standalone antennae. The way you described it makes sense. The third point is the user. Thanks for the other info tho. Gives me a few ideas.

Re:Simple explanation on directionfinding by radio

[Lumpy]

dont even need to be that difficult.

two antennas vertical, standard whips. about 2 feet apart, although 1 foot apart works great.

switch between the antennas at about a 500hz-1Khz speed, not hard at all with a timer/clock chip and a couple of mosfets.

listen to the transmission. you will hear the switching frequency... now rotate the antenna until the tone goes away. That is the direction (or 180 away from it) that the transmitter is in.

but within 30 meters all RDF finders saturate and finding the transmitter becomes skill and cunning now.

Me? I now use a dopplar RDF I got for $150.00 from ramsey electronics. 4 antennas and a 16 led display point the way to the transmitter.

Re:Simple explanation on directionfinding by radio

[Jmstuckman]

If detecting an ADF signal is so simple, then why do ADF systems start at $5970?. Even a GPS system starts at less than half the price.

Re:Simple explanation on directionfinding by radio

[Jmstuckman]

Oops, I see that the cheapest one is closer to $4,520.00. It's still much more expensive than GPS though.

Re:Simple explanation on directionfinding by radio

[afidel]

Because it's a)FAA regulated so there is a lot of sunk cost in getting it certified and b)it's a toy for the rich who are willing to pay for it.

Re:Simple explanation on directionfinding by radio

[Anonymous Coward]

one orientated dead ahead

Orientated? Are you sure? http://dictionary.reference.com/search?q=orientate d

Detect this

[flopsy mopsalon]

I wonder to what extent use of this detector constitutes unreasonable search and seizure.

I pay good money for wireless phone service and I do not need snoopers with "cell phone detectors" singling me out as a potential troublemaker just because I prefer to stay in touch with others by carrying my phone around.

Last I checked this was still the "land of the free". I hope the proliferation of cheap cell phone detectors does not trigger a rash of racial profiling type incidents.

Re:Detect this

[Alranor]

Last I checked this was still the "land of the free".

Just out of curiousity, how many years has it been since you checked that?

Re:Detect this

[Anonymous Coward]

Last I checked this was still the "land of the free".

Free for ownwers of private property such as cinemas to set their rules, you mean? I don't want you in the cinema with me. You fuckling stink.

30 metres?

[phalse phace]

For those who are wondering, 30 metres = ~ 98.43 feet.

1 feet = 0.3048 meters

Re:30 metres?

[Anonymous Coward]

Or, if you're really picky, 30 meters = 98.4251969 feet.

Re:30 metres?

[nkh]

If you want an exact conversion, 30 metres is equal to 3000 centimetres ;)

Re:30 metres?

[hcdejong]

How many shitloads is that?

Re:30 metres?

[Neidel]

Isn't it about time to get of your feet?? - I mean in at time when High scool kids makes James Bond devices :-)

Re:30 metres?

[JaredOfEuropa]

30 metres

I though they were called 'freedom feet' nowadays.

Re:30 metres?

[Patrik_AKA_RedX]

or about 750 chicken eggs.
1 chicken egg == 4cm

or about 166,67 SEDS
1 SEDS (Standard European Dick Size) == 18cm

Re:30 metres?

[Anonymous Coward]

or about 2 SAWS (Standard American Waist Size)...

;p

In HK

[QnA]

In HK, one of the most cellphone popular place, some karaoke do have such facility. Once the detector received any signal from the cellphone, it will display a sign on on the screen and minimize the background sound automatically to avoid effecting the conversation of the phone owner.

Re:In HK

[chaosmage42]

This sounds pretty cool. I don't know if it should be used in a public place where it will affect a lot of people on one persons call, but it could be useful in personal areas, like pausing or turning your stereo down {or pausing your dishwasher - well, not so much a problem for cell phones as for me and my land-lines} when you get a call.

KISS people

[tod_miller]

Just dial their phone and follow the ring tone!

Brought to you by the tin hat brigade.

Where do they hide them?

[tod_miller]

"Prisons are difficult places because they are quite large and cellphones are very small."

If they sold these devices with a pair of rubber gloves, they are onto a winner!

Cell phone noise

[Caltheos]

Hardly a new idea. as a commercial device a bit odd and of dubious use. I know my phone, nokia 3595 i think, makes any amp;lifiers near it buzz loudly when its updating the clock or receive calls. obviously some phones are more suceptible to being pick up then others.

Re:Cell phone noise

[ranebow]

They mention in the article that there are already many of these types of devices out there already, however this one happens to sell for $39.95 NZ compared to $1000!

I remember

[lachlan76]

I've seen something similar to this before. This one however is slightly different (there are two ICs in the one from the article. For those who don't understand electronics, the incoming signal goes into an operational amplifier, and this will compare the incoming signals with that of a fixed voltage (from a battery). This then drives a MOSFET (like a transistor) to switch a load on and off. I would guess that the second IC in the new device is to measure the distance (v x == close) from the signal level). I build the circuit in the PDF, and it has a range of a few meters, but could be improved, if you had the parts/time.

Re:I remember

[Anonymous Coward]

A MOSFET IS a transistor, not like.

Similar one in my car

[tanveer1979]

Whenever my cell phone rings it lights up. But i guess these guys extended the range to 30 meters, rather that standard 2-3 meters you get. Which basically means that in a crowd with around 50 cell phones around you, even if none of them are ringing this device will light up. So not much use as a tracker in such conditions.

But think of buildings collapsed during earthquakes. May be helpful there!

Re:Similar one in my car

[OneSeven]

...........yes.

The first thing that ppl worry about after a building collapse is finding their mobile phones :P

(come on, i know MY mobile is more important to me that human life!!)

Re:Similar one in my car

[yarisbandit]

Ah, but think of people trapped under rubble whose cell phones are still working and on their person - It could help in finding them...

Land of the Paranoid

[CavemanKiwi]

Unless the USA is way behind the time I would say the majority of people have cellphones hence it is similar to people choosing to pick on people with 2 hands. In terms of search and seizure laws I guess this gets a little trickier. My 1st reaction was well your cell is broadcasting so it would the same as telling people to not listen when you are shouting. However what if the equipment would be capable of listening to your conversation that would kind of be spying and I am not so keen on that idea. But is it really different to someone eavesdropping on your conversation in public. So torn. /back to work

Re:Land of the Paranoid

[byssebu]

Eventhough it's illegal (i think) to spy on cellphone-conversations it's very hard to detect and people might even go around listening to your calls already. Not to mention the government, I won't even go into that here :)
I don't know if there is any encryption at all in todays tele-communication but that's the only way to be protected against spying. Preferrably the call should remain encrypted from the caller to the receiver and not just between the phone and the base-station.

Re:Land of the Paranoid

[cpghost]

How long until a master key is leaked from some government agency? Kind of DeCSS for GSM?

Technical article?

[europrobe]

I would assume that this device can also detect when the cell phone does its intermittent "reaffiliation" with the network, since (as others have pointed out) you would otherwise only be able to detect it when it's in use. At which point I wouldn't really need this detector to find out that they have a cell phone.

I do find it strange that they can detect the range to the mobile phone just by using the signal strength. All network standards worth mentioning include the ability for the transmitters to adapt their power depending on the signal strength at the receiver, so signal strength is not a good indicator of distance.

Re:Technical article?

[numo]

I would assume that this device can also detect when the cell phone does its intermittent "reaffiliation" with the network

Yup - normally it does it every few hours. It is possible to force the phone to do this - just jam the frequencies causing it to lose the network. Of course, this would be illegal, as this is a licensed band.

All network standards worth mentioning include the ability for the transmitters to adapt their power.

AFAIR at least GSM uses the full power when negotiating with the network - the adaptation schemes work during the call, but not during the control messages. The effects on my loudspeakers seem to support this theory :-)

Ears

[tiredwired]

Ears are so cheap I got two of them. I can detect cell phones quite well.

Re:Ears

[ravydavygravy]

Ears are so cheap

Really - have you tried buying any recently?

Re:Ears

[boogy nightmare]

really, even when they are set to vidbrate only or silent when the little cheating b4stards are trying to cheat in an exam room...

Re:Ears

[ShawnDoc]

Is it really so hard for the instructor (or TA if at a university) to announce at the beginning of the test that all cell phones must be put away during the test and that if they see one during the test the owner will automatically fail the test. Then all the instructor needs to do is get up every now and then and walk the isles looking for phones. It can't be that hard. I've got my BA and been in more than a few lecture halls. It wouldn't be that hard. I realize some instructors use test time to do work, but most only read magazines or books (or step outside to talk on the phone).

I own the patent!

[spookyfluke]

Ha ha! Time to start sitting back and watch the money roll in! :>

Re:I own the patent!

[Patrik_AKA_RedX]

Too bad I got the patent on rolling money. But for $699... ah forget it.

wow...

[Anonymous Coward]

...you got ISSUES dood. You took a giant flying leap from a kid's science project to RACIAL PROFILING. LOLOLOL! You're a nut. Stay away from me.

Sorry for replying to my own post...

[builderbob_nz]

But I just thought that my comment about being a Kiwi first is probably going to start a huge thread about reading the artical and getting my facts straight. What I meant was that it is a first that it is so cheap $40 compared to $1000. And it is a design so simple that a child could make it (although I must admit that I would have to try an remember which way up you hold a circuit diagram before I atempt it).

Not quite...

[Airw0lf]

It's not just everytime you get a call or text message. Sometimes I hear that sound even though I don't receive a call or a message. It might have something to do with the phone changing from one cell tower to another or something, or simply being polled by the cellular operator.

Re:Not quite...

[ElvenMonkey]

It seems to be a standard thing with mobile phones. At a band rehearsal about a year ago we'd just reached the end of a song when we heard the classic du du du (etc) tone coming from the lead guitarists amp; his phone was sitting on top of it. Then the bassist phone did the same thing to his amp, then the keyboard players, and so on around the room, all within the space of a minute. The sound guy just looked exasperated at us all and rolled his eyes (he's forever reminding us to turn phones off when we rehearse)

Isn't that why the phone rings?

[TheOtherAgentM]

That way you know where the phone is when you get messages or calls. It's always funny to me when the phone rings and someone yells, "Phone!" That's why it rings in the first place.

Creative kids...

[zxflash]

Now if they could only invent something so that when i'm using a cell the person on the other end of the call can actually hear me and not just static and noise... You won't need a fancy device to find me... I'll have one finger in my ear and be screaming profanity throughout the duration of the call... You'll hear me from way more than 30 meters away!

Re:Creative kids...

[hans sprungfeld]

I wonder whether you could do this using a blind source separation algorithm (like independent components analysis, for instance). The statistics of the background noise will be quite different to those of the speaker. Once phones get powerful enough to embed some serious computing in them, you could just have the receiving phone deconvolve the signal into the different sources. The user at the other end could scan through the different sources to try to find the person they're talking to, rather than the train noises. Sounds easy, but I imagine the technical difficulties would be pretty serious.

You insensitive clod!!!!

[Airw0lf]

I'm DEAF, you insensitive clod!!!!!

This looks like a long range version of the...

[alex_ware]

...mobile phone holders that had flashing led's that sold for £1.99

A number of reasons this device might be practical

[SmoothTom]

1) It might detect a cellphone being used for sureptitious evesedropping on a conversation

2) It might detect a cellphone in a silent text ony mode receiving test answers

3) It might detect an active cellphone in a secure environment where they are prohibited

Not all potential uses are obvious ones.

Consider the prison example from the article (You did RTFA, right?) - if prisoners are prohibited cellphones and you detect one in use in a cellblock, it is time to do a detailed search...

--Tomas

What use is a detector?

[Airw0lf]

A detector will tell you that a phone is being used in a restricted area, but it won't help you find it that easily - especially if there are several in a room. The easiest solution for something like an exam room is a cellphone jammer. In saying that, this will only remedy exchange of information via cellphone. It will not prevent people from using their phones as calculators or as notebooks. So if you want to ensure that there is absolutely no cheating in an exam where no calculators are allowed, I would suggest an EMP grenade :)

Re:What use is a detector?

[theCancerus]

detector can give everybody some timepass and nothing else or some can use jammer after detecting the signal
Think of this if we can detect mobile phone in restriected areas then we can start the jammer at that freequecy other wise using jammer all the time will waste a lot of power.

Re:What use is a detector?

[Airw0lf]

But in some situations, detecting a signal could mean it is too late. The person could already have sent/received information they shouldn't have. So for a place where security is critical, jamming all the time might be worth the power wasted.

Re:What use is a detector?

[Secrity]

The legality of your solution(s) would depend upon the laws of the country where the cellphone jammer (or EMP grenade) is located. In a number of countries the use of jammers as you describe would be illegal. If an illegal cell phone jammer is employed for a length of time it is likely that it would be detected and dealt with (the length of time until detection and being dealt with is a variable that depends upon a number of other factors). Personally, I believe that shielding and/or passive jamming of cell phone frequencies is a better option than active jamming -- and it is less likely to be illegal. Some cell phones (Nextel) operate adjacent to public safety (police/fire) frequencies. Jamming of police/fire frequencies in order to jam cell phones is likely to cause the time_until_detection variable to become somewhat shorter.

Re:What use is a detector?

[sexylicious]

Nah. Just sheild the building. Make it a giant Faraday cage and no signal will get out.

Works where I work.

Re:What use is a detector?

[theCancerus]

you are right that under some cirumstances it is better to jam all the time but most of the time it is not required so it is better to a detector before starting a jammer

Alternate suggestion

[TheCyko1]

"Seems like a perfect /.er hack project, and as initiator I get 5% of gross profits."

How about.. no.

detects cheap cell phones?

[Dwedit]

Whoa! I completely misunderstood this based on the headline. I thought it would detect which cell phones were cheap.

It's not so hard

[double_plus_ungod]

once i tried to record a voicemail message using a tape recorder held to the earpiece of my cell phone.

(yeah stupid, but what you gonna do?)

"yeah CLICK we're gonna CLICK go to jack in the CLICKox and we're going to CLICK pick up some more beer... you'd better CLICK not be in lab CLICK or i'm gonna kick your CLICK..."(end message)

detecting that RF bullCLICK should be easy.

WTF???

[Anonymous Coward]

seriously though, a high school student? what are they feeding these kids these days???

Selectivity?

[elgatozorbas]

How selective is this thing anyway? I cannot see anything which might be a filter on the board, so does it only pick out cell phone frequencies? Or also wireless headphones, wireless (non cellular) telephones, wireless car locks,...
Z

Guitar Amp Mobile Detector

[A Boy and His Blob]

My guitar amp, if turned up loud enough, makes clicking noises when I have a cell phone in the room, and it starts buzzing and clicking a few seconds before my cellphone rings. I wonder if this is related.

It's annoying because it does this even if the ringer is off (obviously), and has ruined more than a couple recording sessions.

Re:Guitar Amp Mobile Detector

[LardBrattish]

You leave your mobile turned on when you're recording?!
You're not Frankie "Er Hello Mum, I'm on stage at the moment" Poulain are you?
Seriously, even if you're home recording you have to do your best to isolate the studio from any possible interference, Phones, Taxi Radios, Power tools (unless you're in Einsturzende Neubaten or Slipknot) The phone calls can wait - the perfect take should be what matters

Active connection only?

[dostick]

Detecting active conencted phone is not so difficult. This still does not apply to phone at airplane detection.
Wish they could find a way to detect phone that is not in call.

Selectivity?

[elgatozorbas]

It is a fair warning, but doesn't seem likely that in the next 10 years phones will be able to transmit movies over 'multi-megabit networks', if only because of power constraints. Having you phone ring during the movies is a bad idea already...
Z

Wow

[Anonymous Coward]

they have invented a radio reciever, some cutting edge research in that school

Theater use?

[LostCluster]

The fact that such detectors give out a strength reading that can be used to determine distance gives the opportunity for three or more to be used together in a theater setup. A phone wouldn't even have to ring, just the session establishing contact with the towers is enough, at which point the circles could be drawn to find their intersect point and they'd know where to send an usher to prevent the mid-show interruption before it happens.

Re:Theater use?

[dave420]

Well, a cellphone on silent is no interruption to anyone, so that would be a bit unfair...

Re:Theater use?

[member57]

But when the knucklehead answers it....

Re:Theater use?

[dave420]

Obviously, but text messages are fine in cinemas :)

Re:Theater use?

[member57]

If I owned a theater, cell phones would be banned. I see Dunderheads texting and whatever all during the movie I PAID to watch> I don't want to hear their stupid giggling during the movie. It's simple consideration, if you don't want to watch, then don't buy a ticket and bring your phone to distract me.

Yeh great...

[oliverthered]

Now when my phone is in the glove box and someone trys to call or sends a text I'm going to get arrested.

Re:Yeh great...

[christopherfinke]

You could always try turning your phone off when it's illegal to use it...

Re:Yeh great...

[LetterJ]

I like to at least *know* someone is calling when they call. If it's important (like I'm expecting a call from a client), I can pull into a gas station and call them back. If the damn thing is off, I might not know they called for 45 minutes or more. I'm not going to answer it while driving, but I at least want to hear it ring.

Re:Yeh great...

[Anonymous Coward]

And miss the "Missed Calls" screen?

Re:Yeh great...

[oliverthered]

But I'm not using it so it's not illegal.

RF Interference sensitive areas.

[Fizzl]

Very handy for hospitals whose equipment can potentially be sensitive to the high interference caused by cell phones. (Not going into if they actually are, but when someones life is on line, you don't second guess).

Also for airplanes. As it has been discussed, it's not an issue of interference for the plains electronics, but rather huge stress for the network.
Could be handy to mount some of these at the airplanes ceiling and equip it with a moderately toned piezo buzzer to remind anyone who has forgotten to switch off their phone. Shouldn't get false positives from terminal either while on ground, as the planes are usually more than 30 meters from there.
The piezo buzzer would be probably sufficiently collectively annoying to encourage any bonehead to shut off their phone too :)

(Shameless plug. Check my sig. New release today)

Re:RF Interference sensitive areas.

[alienw]

Very handy for hospitals whose equipment can potentially be sensitive to the high interference caused by cell phones.

Ever see a doctor WITHOUT a cell phone? Most of them carry one.

This is a toy, not a security device.

[bogado]

It will not detect a off device. A bad guy who wants to sneak in and start calls from a secured facility can simply turn off his fone, put it inside a coke can and then turn it on when apropiate.

Re:This is a toy, not a security device.

[Anonymous Coward]

however, it will detect it immediately once it is turned on. For pretty good security, you could hook one up to a cellphone jammer, which will keep the cellphone in question from transmitting untill it is located. Low production cost also means it would be feasable to blanket an entire facility, not just the entrances.

Even more importantly, this could detect cellphone triggered bombs, as they have to maintain contact in order to recieve their order to either explode, or to not explode, as you could rig one with a dead mans switch. (yes, you could set one up to only power up at a certain time, but why then are you not using a timer?)

Cheap cell phone detector- grammar nazi

[panurge]

More useful to junior criminals would be an expensive cell phone detector that only detects triband models with cameras, avoiding the tedium of finding you've mugged someone for a cheap phone.

I think a cheap detector for cell phones is meant.

And now having exhausted the day's ration of pedantry, to work.

How is this news?

[Viceice]

How is this news? People have been selling cheap decorative bands for mobile phones, pens and other items that light up moments before a cell phone lights up.

It's quite popular with the ladies over here and they are onlyh about RM$5 - 20 each.

So these kids put in 4 LEDs instead of 1. Big deal.

I already have a detector...

[Iphtashu Fitz]

Actually I have two - my mp3 player and my walkman. Every time I'm listening to one and my cell phone is about to ring (or another one nearby is) I hear a very distinct pattern of interference in my headphones.

Of course...

[Kjella]

...you're still going to need a damn camera, and be filming with it. I doubt they'll be able to integrate that in the phone with a usable quality, and even if they did it wouldn't be in your pocket. That would pretty much be a give-away even if there's no recording. Combined with some testimony from whoever caught you, I don't think the defense will fly...

Kjella

Re:A number of reasons this device might be practi

[RoosterRuley]

Wasn't there a remotely detonated bomb using a cellphone a while back? Bomb squads could use the device to sniff out transmitters.

No broadcast = No detection

[RogL]

ANYTHING that works by broadcasting a signal can be detected. Cellphone, cordless phone, spark-ignition, even your PC's emissions. That's life; deal with it.

If you don't want "snoopers", don't broadcast. So there's a solution to your concerns: turn off your cellphone when you're not actively talking. Periodically check voicemail, preferably while in a crowded area, where "they" can't track you down.

Comment removed

[account_deleted]

Comment removed based on user account deletion

CDMA

[Detritus]

Another proof of the superiority of CDMA over GSM for cheating :-). GSM uses a modulation scheme that is easy to detect with relatively simple electronics. CDMA phones output a signal that looks like wideband white noise at a very low power level. It's difficult to detect or jam.

Sorry!

[Anonymous Coward]

The government is already on Cola Alert 5. They're watching for those winning Coke cans with the built in cellphone/GPS that can "only" call and transmit to the prize center. Don't think you'll be sneaking a cell phone into a facility inside a coke can, no sir...

Re:The MPAA will be using technology like this soo

[Anonymous Coward]

Nonsense, the same thing was said about mobile phones 5 years ago, and the same BS will be repeated 5 years in the future.

In reality though, 5 years from now, people will still be bringing their hand sized video cams (although possibly they will record to another medium then is standard these days) and just send out the movie from home. Only a complete idiot would even consider using a cellphone to illegally record a movie.

Perfect for teachers

[paulpach]

As a teacher's assistant, I would love to have one of these for those pesky cheaters using text messages.

They've had those for years...

[Transcendent]

...it's called an unshielded speaker. Whenever any data is being transmitted by my phone, my speakers go nuts.

Based on the distance from the speaker (or wire), I can tell how far away the phone is.

On a serious note, the device is simple. The complex part comes in if they can triangulate the actual 2D or even 3D position of the phone, not just the radial distance. Then I'll be impressed...

Waste of time

[GreatBallsOfFire]

It's called a field strength meter, and can be made with a diode, capacitor and typically an analog meter. When the needle deflects, you have electromagnetic energy in the area. Add one or more tuned circuits to it and you narrow it down to the cell phone band(s).

Move along. Nothing to see here.

um and the big deal is???

[grocer]

I have one somewhere...actually it's a pen/cell phone dectector/black light...it's slow to pick up my GSM phone but CDMA pops the light on in about 3 seconds...

Re:Already have one (more of a popping sound)

[mikael]

That happens on our telephone and TV as well. More of a soft popping sound.

Sadly, he lost the competition

[BeatdownGeek]

"Seems like a perfect /.er hack project, and as initiator I get 5% of gross profits."

Of course, this quip made him lose the business competition. If he was a real businessman he would have patented it and charged a 50% licensing fee.

My cheap speakers have done this for years

[gexen]

My crappy speakers make a noise 2 seconds before my phone or my neighbor's cell phone starts ringing.

Already got one

[Anonymous Coward]

Nearly any speaker and my Nextel phone. The speaker to my computer for instance makes some poping interference noise shortly before my phone rings.

Re:A number of reasons this device might be practi

[Anonymous Coward]

No, I didn't RTFA.

Who says RTFA is an requirement for informed debate?
Helpful? Probably. Required? I don't think so.

Posted in true AC style for the inevitable karma-bashing.

This is not a news, why is this info on slashdot?

[asbesto]

there are many circuits on the net that do exactly this stuff, from many years. this is not a news... where are the real news ? why slashdot is decading ? :(

What's needed

[BCW2]

Is a pen sized jammer so that nobody in a 50 foot radius can annoy you with their mindless babble which accounts for 80% of all cell phone use. Mainly for use in resturants, movie or stage theaters,and elevators.

Re:What's needed

[BCW2]

It might have been off topic but it was not flamebait. There is a law in the US that won't allow jammers. Every time a cell phone goes off in a movie there are another 50 - 100 people that want that law changed. There are places where they are banned already, let it sound off in a court room and find out what contempt of court is. The inconsiderate behavior of cell users is what causes the problem.

Useful for road-side bombs and other

[vashathastampedo]

Asymetric attacks. Most of these are set off by cell phones. Granted this doesn't really give you much of a warning.

Can you detect a phone that isn't being used?

How about an RFID detector?

[Anonymous Coward]

That would be useful!

Speakerphonedetector

[zerocircle]

I already have one, its a set of speakers on my desktop. Everytime a cellphone gets a call/text i get a:

dicky-dick-dicky-dick-dicky-diiiiiick

Yeah, me too, but it's not only during a call or text. Apparently, my phone (a Nokia 6340i on Cingular) periodically contacts the network -- either it's auto-setting its clock or just checking in with Big Brother. For a while, at first, I had no idea why I was hearing these weird little chirps from my speakers, until I noticed they also happened right before I received a call.

In the classroom

[enigmax01]

I can see this technology being implimented in the classroom where most mobile devices are prohibited, especially in high-schools. Professors get sooo agitated when someones cell goes off... This may help them in detecting if students are messaging during class... or even worse... a test.

I'd buy a cheap jammer

[peter303]

A hundred dollars or so.
Evenif it was illegal.

Re:I'd buy a cheap jammer

[Anonymous Coward]

Make one!

900 Mhz. Colpitts Oscillator.

Power from unfiltered DC fresh from the power supply rectifier. This causes the Colpitts oscillator to both frequency and amplitude modulate to 60/120 Hz.

Literally wreaks havoc within its range.

And its cheap enough to build that if someone finds it and destroys it, you haven't lost much.

You can get enough power from a doorbell transformer to ruin cellular reception for a good-sized theater.

Why???

[ranolen]

Why would you need this. I can detect a cell phone without it. Look at a person... cell phone detected. Everyone has one now, including 6 year old kids.

For the god's sake that was just a school project

[Anonymous Coward]

There is nothing special about the device. Anyone with 3+ years experience in electronics can draw a schematic for such a device in 2 minutes. The problem is that it you'll get a lot of false positive detections because the device will pick up noise and interference from other electonic devices as good as it does from cellphones.

*Cough* OT...

[sexylicious]

Civil Aviation Authority's experimental results for cell phone usage.


The CAA is the British equivalent of the FAA. The FAA has not done the same tests for itself. Instead it has relied on the CAA's data and erred on the side of caution.

And not all of the avionics are located on the flight deck. The avionics, especially things like flight control computers, are distributed throughout the aircraft in a redundant system.

Jammers violate FCC regulations

[KenSeymour]

An excerpt from an article in slate:

In the United States, actively jamming a cell-phone signal is illegal. The FCC, which is the government agency in charge of regulating the airwaves, has established severe penalties for doing so. If you're caught at your local restaurant with the SH066PL2A/B, it's possible you could face an $11,000 fine and a one-year jail term. Possible, but apparently highly unlikely. It seems that the FCC has never charged anyone with this crime, even though the American market is one of the most important when it comes to selling cell-phone jamming equipment. One distributor (who wished to remain anonymous) told me they've exported approximately 300 jammers to the United States this year, more than to any other country. The exporter claims that buyers include restaurants, schools (including some universities, which have installed the technology to stop students from wirelessly diddling away on their phones during lectures), and personal users.

More than cell phones...

[Ancient_Hacker]

Hard to tell from the pictures, but it's unlikely to be a very selective receiver. Which suggests it's going to have a large false-trgger rate from nearly any RF emitter, such as wireless doorbells, wireless thermometers, wireless lightswitches, old flourescent bulbs, police and fire radios, gas meter telemeters, garage door openers, wireless headphones, and even wireless network hot spots. Needs a little work.

WOW

[Hotrodder]

"works by picking up the bursts of radio frequency activity"

Wow they invented the radio receiver.

Cheap cell phone detector

[Anonymous Coward]

This is great! I am annoyed by all those cheap models. Can't wait for an expensive model detector though. :-P

Should use them in movie theaters.

[Axe]

And automatically shoot the bastards.

What use is this thing?

[YrWrstNtmr]

It got them a win in the competition.

Re:The MPAA will be using technology like this soo

[Idarubicin]

Give it 4 or 5 years, and mobile phones on new generation networks will have high resolution image stabilised digital cameras and the ability to transmit this image in real time, already compressed, down multi-megabit networks.

You just need to look for the person with the backpack-sized battery....

Such a phone would video a movie from a pocket, and there would be no evidence, because it would be transmitted away.

But why would anyone want full-motion stabilized video of the inside of my pocket?

Coming soon: triangulate and exterminate.

[twitter]

Actually, I'm told by pot secret sources, that the MPAA has a much more advanced system. It consists of multiple receiving units, so that the position of the phone can be known to three feet. X ray lasers are slaved to the devices output and will vaporize anyone in the area, so as to make an example of any doctor, firefighter or other emergency responder dumb enough to go to the movies.

I do exactly that if I use the hands free...

[Ayanami Rei]

and usually people can detect it. About 30 seconds into the conversation, they'll ask, "Are you in the car?".

But sometimes they'll say that while I'm simply walking outside and trying to not get hit in a parking lot...

cool...

[bagofcrap]

Now if only they had hooked it up to a really distracting flashing bunch of LEDs...

Then, as its so cheap and easy to manufacture, they could start putting them into everything... like cellphone antennas and stickers and such...
Then you could sell them at the cell phone booths at mall for $20.

gee.

5%? I call PRIOR ART!

[blair1q]

Just about any set of self-amplified multimedia speakers can detect cell-phone transmission bursts if the phone is held reasonably close (within a foot or so).

Designing an RF section to cover the cell bands would easily give the thing range in the 10's of meters.

So it's obvious, and you get nada.

Are these electromagnetic bursts...

[generationxyu]

...why the TV starts buzzing a couple seconds before my phone rings?

get a better phone

[Anonymous Coward]

my phone will start ringing audibly
if it receives three phone calls from the same number, which after ringing are directed to answering machine, and I never touch(push buttons) the phone

This of course is no help if the phone is off

Comment removed

[account_deleted]

Comment removed based on user account deletion

I wonder how this would behave in China...

[toogreen]

I am currently working in Shanghai, China... And considering the amount of mobile phones around here I really wonder how efficient this device would be here! I mean there's probably something like an average of 3 mobile phones every square meter... So I would imagine the device would just panic and blow up or something!!

Great...

[Eternauta3k]

it's enough to track, say, a software patent violator in the woods

Now you've ruined our protection from SCO!