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burglar cell phone sniffer

capture the data coming from the burglar's pocket
  (+10, -6)
(+10, -6)
  [vote for,
against]

A cellular phone broadcasts information all the time. When you turn on the burglar alarm, a sniffer is activated to trace mobile phones. Your phones are known, but other ones are not. When an unknown phone moves across the lawn, the alarm system alerts you.

The first couple of weeks you should learn it the phone-IDs of the newspaper delivery boy, the milkman and so on, but after a while it will become quite smart.

If a cell phone also broadcasts its number (not sure) it would be cool to call the burglar while he is downstairs. Tell or text him he should better just leave and close the door behind him.

After a while the burglars know they should turn off their phone before going to work, but they will probably forget. If they were the disciplined kind they would work on the other side after all. "Been stealing again?" the misses asks in the morning, "I tried to call you but your phone was turned off again."

The product will be most reliable as an extra service from an existing cell phone provider, they have the know-how and the technology after all.

rrr, Feb 20 2006

Stalker Detector Stalker_20Detector
[theircompetitor, Feb 20 2006]

Cell Phone Tracking http://www.msnbc.msn.com/id/11273089/
..in Britain. [DrCurry, Feb 20 2006]

Engadget: "World Tracker turns anyone into a cellphone spy" http://www.engadget...to-a-cellphone-spy/
Heck, Britain is pioneering the use of cell phone location. No GPS or anything else required, just tower data. [bristolz, Feb 20 2006]

Comment from former Vodaphone employee http://www.engadget...lphone-spy/#c955701
Seems to me that not only is it used but its mature and works whether the phone is on or off. [bristolz, Feb 20 2006]

Check: does your phone have E911? http://www.legalaff...oerner_julaug03.msp
[Ling, Feb 21 2006]

Tracking via cell phones http://news.com.com...1039_3-6038468.html
[hippo, Feb 22 2006]

Detect cell phones http://www.cellbust...h=21&products_id=28
$595 Cell phone detector [zigness, Feb 23 2006]

Location Detector http://www.ece.vt.e.../ar04/detector.html
More "magic" [zigness, Feb 24 2006]

Cell info on the Cornell University site. http://www.cit.corn...phone/security.html
more interesting info... [zigness, Feb 24 2006]

Services to track mobile phones in the UK http://news.bbc.co...._online/4747142.stm
Different - but interesting [Jinbish, Feb 27 2006]

[link]






       RING! RING! <whispered> 'I told you never to call me at work! Um... Gotta run now.'   

       //learn it// sp. 'larn it'
spidermother, Feb 20 2006
  

       But it'll never catch dishonest milkmen.
coprocephalous, Feb 20 2006
  

       The cell phone must broadcast something, otherwise every cell tower would try to call the same phone. It's probably coded, however.   

       The code need not be immediately unscrambled, just record it and play it back to the cell phone company under controlled conditions (police present; court order; whatever). Let the phone company unscramble it.   

       Chances are that the thief has previously stolen the mobile phone...
Ling, Feb 20 2006
  

       //A cellular phone broadcasts information all the time//
Yes but it's encrypted, so unless you have a very clever sniffer (please provide details) this wouldn't work....

//If a cell phone also broadcasts its number (not sure)//They don't.

//The product will be most reliable as an extra service from an existing cell phone provider, they have the know-how and the technology after all.//No they don't. In order to track a mobile through a neighbourhood you'd have to have a cellular network that mapped a separate cell to each house. This ain't how it works. Even then, the vagaries of RF are such that you couldn't be sure that a phone receiving service from a house's cell wasn't actually in another house or yard.

It's a nice idea but it's not as easy as all that unfortunately. [marked–for-deletion] magic.
DocBrown, Feb 20 2006
  

       [DocBrown], I think the idea is to capture the mobile signal directly using some kind of receiver in the home.
Ling, Feb 20 2006
  

       //I think the idea is to capture the mobile signal directly using some kind of receiver in the home// In which case it would have difficulty distinguishing between a low-power phone nearby, and a higher power phone further away.
coprocephalous, Feb 20 2006
  

       I got that [Ling] but you'd still need to use the correct protocols, or phones wouldn't respond. This limits you to working with the existing network infrastructure and, as I noted, it's simply not organised in a way that would facilitate this scheme.
DocBrown, Feb 20 2006
  

       I think the idea is a good one, and I can't see why it wouldn't work: double the distance requires 4 times the power. For example, if I put my mobile on a stereo system, I can hear the chirping easily, as it communicates with the network. The most powerful mobile couldn't do that even if it was only a few metres away.   

       But if you mean the difference between 30m and 40m, then I agree it would be difficult to distinguish. But I don't think that's really a big problem if you want to check who is in the house, or next to the house.   

       edit (crossed notes) [DocBrown], the system would need to be passive, and rely on the broadcast of the mobile. I'm not sure what triggers the mobile broadcast: it could be after detection of cell. Some kind of signal blocking/ unblocking might trigger the broadcast?
Ling, Feb 20 2006
  

       Given that you can buy cell phone repeaters/signal amplifiers for use in the home, I imagine you could mod one of those to achieve this.   

       DB/cp: while there might be a lot of false positives from more distant phones, it would limit the search sufficiently for the police to identify the culprit after a break-in or series of break-ins. I like this idea.   

       I dispute that MFD. The device would also come in handy for the blackmailers amongst us (except I think they already have the equipment to do this).
DrCurry, Feb 20 2006
  

       [DocBrown]. First of all, this is a LONG WAY from magic. Please remove your MFD.   

       I'm very careful to make sure that I really do know what I'm talking about before I drop an MFD on an idea. I'd suggest you do the same.   

       This is completely do-able. All that is required is information regarding the encoding/decoding of the signal (the cell companies have this) and correct placement of more than one antenna on the property for triangulation.   

       The phones broadcast their ID which, while not the phone number, performs the same basic function.   

       In other words, I could put my phone in a pre-defined location that the system would recognize and turn it on to train it for that phone. Repeat that for all phones that are "known". Any other phone that triangulates to match a location on the property would alert the system to activate the alarm.   

       //In order to track a mobile through a neighbourhood you'd have to have a cellular network that mapped a separate cell to each house. This ain't how it works. Even then, the vagaries of RF are such that you couldn't be sure that a phone receiving service from a house's cell wasn't actually in another house or yard.// Not true.   

       p.s. My cell phone is already triangulated by the cell company with enough accuracy to tell which house I'm in.
zigness, Feb 20 2006
  

       [DocBrown], //... but you'd still need to use the correct protocols, or phones wouldn't respond. This limits you to working with the existing network infrastructure// Why does this limit you to working within the existing network infrastructure?   

       //...as I noted, it's simply not organised in a way that would facilitate this scheme.// We need some details here because my knowledge of the system (and radio and communication technology) says otherwise.
zigness, Feb 20 2006
  

       [zigness], apologies for not offering a fuller explanation of the MFD. I'm sort of busy and didn't think anyone would want to read it anyway. Here goes:
//All that is required is information regarding the encoding/decoding of the signal (the cell companies have this) and correct placement of more than one antenna on the property for triangulation.//The cell companies encrypt their communications with phones using algorithms defined by the telecommunications standards employed (in most areas GSM, although 3G is becoming more and more common). In order to communicate with a phone using such algorithms you'd have to operate a basestation. As noted, for this scheme to work, you'd need at least one basestation per property, probably more like 3 in order to perform accurate triangulation. Immediately, the idea becomes economically ridiculous since you're now talking about 3 basestations per house. The cell phone companies aren't going to put in that kind of capacity to have it uselessly standing idle so you're now asking consumers to absorb the cost. Highly prohibitive to take up methinks.

//The phones broadcast their ID which, while not the phone number, performs the same basic function.//Not really. Phones don't broadcast anything until they detect the signal of a valid basestation ie. one belonging to the network they belong to. Even then, to avoid sniffing by potential phone cloners, temporary identities are used. These temporary IDs change frequently and would make it impossible to vet phones on a known/unknown basis since all your sniffer would see is a bunch of temporary IDs signing on that it had never seen before and would never see again. Oh yeah, re-read that bit about phones only responding to the network they belong to. If we assume there are 4 GSM networks operating in the area that increases the number of antennas required to 12, plus whatever you want for 3G. If I'm a good burglar at this stage, I'm avoiding the houses with 12+ antennas on the roof, or just using a PTT radio.

//My cell phone is already triangulated by the cell company with enough accuracy to tell which house I'm in//How nice for you. This is possible, but relies on extra hardware in the phone that isn't standard under GSM, although legislation in the Land of the Free(TM) and Japan will shortly make it legal for all new phones to incorporate it. Again, if I'm a smart crook, or even a slightly clever one, I'm not opting into a tracking system.

Hope this has made the case for the MFD a bit clearer. The idea itself offers no answers to the obvious technical obstacles, to say nothing of the monstrous waste of money and RF capacity implied.
DocBrown, Feb 20 2006
  

       DocBrown: any way you look at it, it's not magic. The idea may just need a little modifciation to be workable.
DrCurry, Feb 20 2006
  

       I'm agreeing with DocBrown about this not working. I don't say it's magic, though, I just say there is a large misunderstanding of cellphone operation.   

       DocBrown describes the problem, but doesn't call enough attention to it. The problem is this: An idle cell phone doesn't broadcast anything continuously. People just assume it does, for some reason.   

       A cell phone only communicates with the towers at two times. Obviously, when it's being used for a call. Second, and sometimes simultaneously, when it's picking a tower.   

       What a cell phone does when you turn it on, is to listen for a tower. When it hears a tower, or more than one, it picks the best signal, then it broadcasts a message to that tower and identifies itself. The entire system then knows to route all calls for that phone to that tower's cell of coverage.   

       The phone then goes to listen-only mode. All it does is keep checking to see if it can still hear that tower, and whether that tower is telling it that it has a phone call. It does not have to broadcast anything.   

       If the tower's signal drops below a certain strength, the phone then starts to listen for stronger tower, signals that tower that it wants to log in to that cell, then goes back to just listening to that new tower. The system routes calls for that phone to that new tower/cell.   

       There is a lot of encryption and temporary IDs involved, but I don't need to go into that. The short version is, an idle phone does not send out a signal. There is nothing to track.   

       The system as a whole only knows which cell the phone is in. The Cell Phone Tracking link above says the following: "It tracks cell phone SIM cards with accuracy that varies depending on the saturation of SIM masts — in city centers the technology can pinpoint a phone to within a hundred yards, while in rural locations it might be several miles.'' In other words, it knows which tower is taking your calls, and that's all.   

       Other evidence that a phone is not continually broadcasting can be found in the fact that a phone call, when it actually is broadcasting, uses up the battery a lot faster than just listening. Also, the signal strength monitor is in the phone to notify it to check for another tower--showing you the signal icon is just an extra feature--if your phone was broadcasting continuously, the towers would monitor it, instead.
baconbrain, Feb 20 2006
  

       By now it is obvious it is a product only the phone companies can develop.   

       >Oh yeah, re-read that bit about phones only responding to the network they belong to. If we assume there are 4 GSM networks operating in the area that increases the number of antennas required to 12<   

       Is that also the case in Europe? When I go to France with my GSM I have 4 networks I can choose, there are roaming agreements with all of them. There are also virtual network providers signing agreements with all kinds of existing providers, so I am sure they can sort that part out if some party shows up with a solid business model.   

       Setting up 3 of those base stations is a bit overdone I would think. Just one centrally in the house is enough I would say. It only wants to know about the phones in the direct proximity, nothing more.   

       Perhaps these base stations are expensive now, but prices will drop if they can be employed everywhere. Think not only about consumers for this but also other places that want protection from unknown visitors.
rrr, Feb 20 2006
  

       How about simplifying it? Cell phone detectors exist, one can buy them easily on the web. Some theatres use them with an automated system that asks the patron to turn off the phone. Yes, they don't capture the specific phone ID only the fact that they are on and in close proximity.   

       So, you have such a system in your home and it is manually armed and disarmed by the resident upon exit and arrival. Once armed, and after detecting any cellphone in its immediate proximity, it waits a minute or two and then silently calls in an alarm. The police arrive and capture the cell-phone toting burglar.   

       Alternatively, the detector could notify the cell phone system and report its location and the cell phone system can resolve the individual phone against the location and identify the phone. The location is derived from first determining the cell the phone is in (and this info is seeded with the detector reporting its own location) and then three tower triangulation is done using difference of arrival (TDOA), which calculates a phone's position based on the speed the signal reaches multiple nearby antennas, and angle of arrival (AOA). With AOA, cellular towers identify the direction from which a signal is coming and then plot the direction of the incoming call based on a reading from two towers. No special client-phone capabilities or equipment is needed for either or both of these methods to be used to determine location.   

       This identification is logged for law enforcement queries. A subpoena produces the record for law enforcement.
bristolz, Feb 20 2006
  

       I guess that would have the advantage of not being triggered by deer wandering about the garden. But I thought the argument above was that call phones are passive devices when not searching for a signal or being used for calls?
DrCurry, Feb 20 2006
  

       They can certainly respond to a cell system "ping" and that is all that is needed. Besides, if they were "passive," cell phone detectors wouldn't work and they do work, I've been in their presence when they are working. Maybe the phones are passive to the cell system--I have no idea--but they aren't absolutely passive.
bristolz, Feb 20 2006
  

       I think the trick could be as follows:
When the house alarm is on, have a temporary cell phone jammer, which pulses on and off. This causes a local mobile phone to lose the net. When the jamming is removed, the cell phone logs on again.
I presume the cell phone can only initially log on using a known ID, which must be related to your SIM card and possibly the ID number of the phone itself.
I don't think triangulation is required, if a local sniffer is used, since signal strength would imply proximity.
Ling, Feb 21 2006
  

       Of course, given that the burglar is probably carrying a stolen phone in he first place, this may not be much use anyway...
DrCurry, Feb 21 2006
  

       Thanks [bristolz] for putting up an accurate depiction of how cell phones function. You've saved me a lot of typing this evening.   

       Again, [DocBrown], you've made some assumptions that are simply not completely correct -- MFD for "magic" is completely out of line with this one. In fairness, please kindly remove it.
zigness, Feb 21 2006
  

       I haven't seen any evidence to warrant removal of the MFD [zig]. To quote the help file: " magic- the author is using a technology they know very little about as magic. This imparts superpowers, among them the ability to always know where something is"

That is exactly what is going on with this idea. The big problem with it, as [baconbrain] spotted immediately and [DrC] cottoned onto as well is that phones don't broadcast signals unless prompted in a pre-defined manner which is only employed by basestations. Furthermore, a phone will only respond to basestations broadcasting its home network's signals. To emulate such a signal, as I explained above, you would need a minimum of one basestation per network in operation. Neither the main idea nor [bristolz] amendment solve this problem.

The second problem is that phones do not broadcast their identities, so you're immediately reducing the system from something that will tell you if a strange phone is in the vicinity to something that will tell you if a phone is in the vicinity. When you factor in the difficulties inherent in accurately delimiting RF emmissions (a bit like trying to herd cats or smoke)what you're left with is a system that might be able to tell you there's a phone in your house, or maybe on the pavement outside, or in the next door neighbour's garden, or a passing car. Not much good for the stated application.

The passive cell phone detectors that have been referenced simply look for the presence of correctly modulated energy in the relevant part of the spectrum. They could be used for this application but again, would only inform you of the presence of a phone, not identify particular phones. If you like windows in your home, it's going to be tough to seal it off to RF energy, so again you'll be seeing a load of false positives from phones not on your property but in your general area.

If you want to keep discussing this I'm keen but please rid yourself of the inaccurate preconception that mobile phones are forever sending out some kind of easily measurable beacon pulse, containing their IDs and user information. Methinks you've watched "Enemy of the State" a few too many times.
DocBrown, Feb 21 2006
  

       Doc, I think you're being too enthusiastic in opposition. One might argue that you can even alarm off a bluetooth or wifi signal from today's phones   

       Though a smart burglar might consider turning the phone off for the same reason they ask you to do it in theaters
theircompetitor, Feb 21 2006
  

       I really don't think I am [tc]. I'm basing my argument on a moderate level of knowledge about the technology in question, whereas certain other people seem content to fill in the gaps in their understanding with details that conveniently enable this idea to function.

I guess you could alarm off WiFi or bluetooth but I've yet to come across a phone where these are always-on functions. Wait a year or two for the first multi tech phones and then maybe you'll see some like that, but not at the moment.
DocBrown, Feb 21 2006
  

       Fill those gaps they may, but this the HB, not the patent office.   

       Since we're not making this personal, I won't mention my four telecom patents and the fact that I run a company developing software for cellphones :)
theircompetitor, Feb 21 2006
  

       Well given what you've just not mentioned, you know better than me why this won't work [tc]! Which company btw? Were you at 3GSM?

I always read "Half baked" as implying some measure of plausibility that this just doesn't have for me. Ideas in other areas where expertise is commonly held (automotive, computing etc) don't get away with sloppiness so I don't see why this should be any different.
DocBrown, Feb 21 2006
  

       Yeah, but in the end, it's the admins who decide if the MFDs stick, and you've got on of them arguing against you above.
DrCurry, Feb 21 2006
  

       magic just seemed a bit strong to me   

       company in my profile -- last show i was at was ctia in san fran, couldnt get away otherwise
theircompetitor, Feb 21 2006
  

       Cool. I'll take a look [tc]. Magic does seem a bit strong until you get down to the nitty gritty but that's what they're asking for unless they make concessions that significantly alter the idea (no IDing of phones, no strictly delineated system boundaries)

I presume that'd be [bristolz] [DrC]? I'm hoping she'll take note of the points I made in my last long post. Regardless of her decision I know I'm right, MFD or no MFD. Would be nice to be able to convince a few other HBers of that, but if not it's cool. Tis only one idea.
DocBrown, Feb 21 2006
  

       Just a friendly reminder this is the *Halfbakery,* not the Telecom Industry Insiders Forum. [Then again, of course, I did get a bit apopletic about some jackassedly wrong-headed idea the other day - it's easy to do.]
DrCurry, Feb 21 2006
  

       I know, and I'm really not upset about the idea. What compelled me to defend my reasoning in the first place was [zigness] telling me I wasn't right to MFD and that I didn't understand how cell phones work. I've said my piece so I plan on shutting up now, unless someone comes back with a load of stuff about how I'm wrong and such, in which case my inner argumentative will probably take the controls again. I try, I really do, but I love arguing too damn much, especially when it's something I actually know a bit about for a change!
DocBrown, Feb 21 2006
  

       Makes for good discussion.
bristolz, Feb 21 2006
  

       OK, Doc... Here goes...   

       First, mounted on the home property are three low power radios set up at various points and broadcasting on a frequency in the available frequencies of cell phones, and one not in use in the current cell in which it is situated.   

       At least one of the radios periodically transmits a System Identification Code (SID). This is a 5 digit number that is used to "ping" the cell phone. Our imaginary alarm system would be assigned one of these numbers. Since there is no need to link this back to the cell system at large, this would be a cheap radio -- on the order of a few bucks.   

       This would cause the phone to respond, which is simply a transmission of a radio on a particular frequency. At this point, the three receiving antennaes could triangulate (using nothing more complex than simple loop antennaes similar to the ADF system on aircraft) to locate the phone.   

       If the locations of the other "allowed" phones were already known and tracked, then any new phone would show up as an "intruder".   

       At this point, it's a relatively simple software problem -- no magic required.
zigness, Feb 21 2006
  

       [zig], your solution would definitely work *if* you could retrospectively engineer all the cell phones currently at large to respond to your SID ping. I'm assuming you don't have the resources to do this so what you're effectively stating is that this is a simple software problem if the Giant Telecomms Fairy can find it in her heart to descend from the sky and make the necessary alterations to an estimated 1.65 billion mobile phones (stat. source GSM world association estimated customer figures, assume each customer has only a single phone)at large. She might be happy to do that, but if she is, she's definitely going to use magic!

This system could work but only with alterations to an enormous amount of pre-existing technology (ie. every mobile phone on planet Earth). I might as well propose a hot air balloon that could reach the Moon. All I'll need is a slight extension of Earth's atmosphere and a minor tweak to gravity....
DocBrown, Feb 22 2006
  

       Quite a simple solution:   

       When a mobile phone talks with a base station (either receiving a SMS or simply paging) the RF signal can be picked up by normal, run-of-the-mill, common garden speakers.   

       Therefore, install loudspeakers throughout your garden. Supply them with power but no data signal. As a protagonist tries to lurk in your garden, his phone will now give him away!   

       QED.
Jinbish, Feb 22 2006
  

       From what I have just checked, when a cell phone is switched on, it checks for an SID. If it cannot find the correct one, it displays 'network not available'. However, if it finds one that is correct, it registers itself, which requires the phone to transmit some data, such as it's MIN.
Cell phones also re-register approx every 10-20 minutes, depending on the service provider set-up.
  

       Now the big question is, if you jam the SID by locally transmitting on the same frequency, then take away the jamming, does the phone see the SID appear and then try to register itself? If so, the (encrypted?) data can be recorded for decoding or whatever, later.   

       This is not 'pinging' but basically fooling the phone into thinking that it has re-aquired the cell signal, and thereby controlling it's registration process.
Ling, Feb 22 2006
  

       That might work [Ling] but you're still limited by the fact that a phone will only attempt to register with a basestation that's transmitting the signal of the network it belongs to. This, plus the fact that accurate location resolution was in the original remit puts you back in the territory of 3 basestations per network. That'd be 12 around my neck of the woods to cover all four networks. Plus different manufacturer's phones behave differently with respect to re-registering after a period of no coverage. Some would behave as they should and periodically re-attempt registration, others wouldn't do anything until they were power cycled or manually prompted to search for networks.
DocBrown, Feb 22 2006
  

       //your solution would definitely work *if* you could retrospectively engineer all the cell phones currently at large to respond to your SID ping// - and -   

       //That might work [Ling] but you're still limited by the fact that a phone will only attempt to register with a basestation that's transmitting the signal of the network it belongs to.//   

       It's clear to me, [Doc], that you have no clue how cell phones really function -- in particular, as it relates to "roaming". If my cell phone worked the way you describe then I failed to make about 100 calls that I remember making last month while not registered on my home network. As a matter of fact, I can't even use my "home" network where I live, but yet I persist at making and receiving calls.   

       For some reason you've got this idea that the ONLY way to detect a cell phone is if it's "registering" through a standard channel. It's just a radio for goodness sake!   

       Ping It... Detect it... Track it...   

       No telecom fairies required. No magic necessary.   

       //This system could work but only with alterations to an enormous amount of pre-existing technology (ie. every mobile phone on planet Earth). // Bullshit.   

       This argument is proof yet again that a little bit of information in the wrong hands is a very dangerous thing.
zigness, Feb 22 2006
  

       // No telecom fairies required. No magic necessary.//   

       Nope. Just some loudspeakers.
Jinbish, Feb 22 2006
  

       //a little bit of information in the wrong hands is a very dangerous thing// I couldn't agree more [zig], but from a very different perspective. I'm not sure the fact that you've learnt that cell phones are "just radios" convinces me that you are the authority here.

Your roaming anomaly is easily explained. A phone holds on its SIM card a list of networks which it may access, in priority order. In the HLR (a giant database in which a network operator keeps subscriber details) there are further details pertaining to roaming and whether a particular subscriber has roaming rights etc.

When a phone scans an area on power up, it uses the list on the SIM to determine which operator to sign onto. If it finds its home network, it will sign onto that. If it doesn't, it will use one of the others on its list or, if none of the networks on its list are available it won't attempt to sign on at all. This third case is what will prove the undoing of this idea - the fact that unless you present a phone with a valid network signal it won't respond/ping or whatever. I don't know what the local situation is where you are, but in general network operators don't sell phones/SIMS that are network agnostic, because it makes bad business sense - the network operators want their phones to be on their network making money for them as much of the time as possible. So if you configure your sniffer to send out one network's signal, you won't detect phones on other networks.

Given that you can't just send out a unilateral request and expect all phones to respond, you're back to using twelve antennas to cover them all and (if you check all the way back) using temporary IDs, which means you can't tell the difference between your phones and ones that have just handed off from another cell.

I've tried to make this as clear as possible, hope it makes sense to you.
DocBrown, Feb 22 2006
  

       //That might work [Ling] but you're still limited by the fact that a phone will only attempt to register with a basestation that's transmitting the signal of the network it belongs to.//   

       //When a phone scans an area on power up, it uses the list on the SIM to determine which operator to sign onto. If it finds its home network, it will sign onto that. If it doesn't, it will use one of the others on its list or, if none of the networks on its list are available it won't attempt to sign on at all.//   

       I think the second statement is more accurate, and I agree my solution will not work if the phone is not in a valid network area. But in my neck of the woods, roaming is more or less complete across all network providers - lucky me!
Ling, Feb 22 2006
  

       The second statement is the full picture, yeah. I'm curious [Ling] - does every operator in your area allow their phones to sign onto all other networks then?
DocBrown, Feb 22 2006
  

       Doc, you've pretty much guaranteed I won't delete this by fomenting an interesting and informative debate. Content is king and all that.
bristolz, Feb 22 2006
  

       Fair enough [bris]. You understand, of course, that I can't remove the MFD for fear of being seen to concede :)
DocBrown, Feb 22 2006
  

       Heh.
bristolz, Feb 22 2006
  

       //I'm not sure the fact that you've learnt that cell phones are "just radios" convinces me that you are the authority here.// [Doc], I'm afraid that I've "learnt" a lot more than that about cell phones.   

       There are things that you've said that are simply not true in terms of how the system and individual cell phones currently work in the United States (which is where I am).   

       Since you've stated (in effect) that you're not going to remove your MFD regardless of whether you're actually right or not, I'm simply going to move on to other things. Enjoy all... this one was fun.
zigness, Feb 22 2006
  

       Just as an aside... why would a burglar have a phone on him and turned on at the same time? Oh, nevermind... :)
zigness, Feb 22 2006
  

       [zigness], you keep stating that you understand how phones work, but it's not terribly convincing when every response to a technical explanation I provide is met with some variation of "You don't understand cell phones, I do, they're just radios". They *are* radios but they operate under a strict set of protocols which you seem hellbent on ignoring. Unless you work with these protocols and provide the phones with signals they can understand you will get nothing back.

In addition, please take note of the difference between removing the MFD for the sake of a bit of peace and admitting that I'm wrong. As it happens, I'm too stubborn to do either, but that's by the by!

I think we'd both agree that on one side of this argument we have a person who understands how these things work, and on the other side we have someone who doesn't, and refuses to accept that their view of things is wrong. It's possible to use a word as absolute as "wrong" because we're debating the behaviour of phones as defined by a specification. You are either correct in your understanding of the specification, or you are not. I can assure you that you are not correct, though you seem unlikely to be capable of accepting this. Since it seems beyond my powers of persuasion to convince you of your error, I'd suggest you look for some reference material on GSM and phones in general and have a read.
DocBrown, Feb 23 2006
  

       I can just imagine DocBrown in Marconi's laboratory: "No, no, you simply don't understand, telegraph protocols simply can't accommodate the information you need for moving pictures!" [splutter]
DrCurry, Feb 23 2006
  

       Nice [DrC]. I'm not that old though!
DocBrown, Feb 23 2006
  

       Alright... I couldn't leave this alone...   

       [Doc], check the link I just added above.   

       Here's what I can do.   

       I'm going to buy 3 of these devices (or two) -- install loop antennaes (which I know how to do)... then I'm going to send the results of each to a base computer for triangulation. (I know how to do that too since I've been writing software since the late 1970's -- I was a kid then and taking classes at a local college -- more recently, I own a software company as well as two other high-tech ventures).   

       Now, according to the FAQ on this company's website, I can now detect 90% of existing cell phones within about a 100 foot range. Interestingly enough, this even works for phones that are in standby mode (I knew that it would -- despite your insistence to the contrary).   

       So, since I can now detect the phones and triangulate the phones -- care to take a stab at how loop antennaes work? -- I can track the phones. All for under $2,000.   

       I've been exploring the development of a patent application for a device that would work somewhat differently but would compete with the above referenced device, so I'm just simply not going to explain anything more than that about it.   

       So, as I see it... you've got some "conceptions" about how cell phones behave and you've jumped to the conclusion that because you can't imagine a solution, there must be no solution -- therefore, it's "magic".   

       The truth is, I can think of at least 8 distinct ways that this idea could be implemented with various levels of success -- all using off the shelf components and custom software. (Please argue with me about software -- please!)   

       None of them require magic.
zigness, Feb 23 2006
  

       Finally,   

       [DocBrown], moving back to the beginning of all of this... you said the very idea is "magic", and you tried to put up a bunch of technical hoo-ha about "standards" to "prove" your point.   

       Well, it didn't work. The link I posted is for a $595 dollar device that will detect cell phones -- even in standby mode. It just won't tell you where they are on a coordinate grid -- just that they are roughly within a certain, small, radius.   

       This, off-the-shelf device, accomplishes the nature of this idea.   

       How very odd to find a device for only $595 that actually does what the good doctor claims to be "magic".
zigness, Feb 23 2006
  

       Sorry to butt in on this rather impressive debate, but your link would appear to be detecting cell phones in general [zigness]. This idea suggests a device that can track specific phones.
hidden truths, Feb 24 2006
  

       [hidden], I explained that. Loop antennaes on no more than two of the devices could locate the phone. And that's WWII technology -- certainly not magic.   

       I agree with you that this idea calls for location information, but Doc's assessment was calling for even these cheap detectors to be termed "magic". (I won't even start talking about his "twelve antennae" requirement.)
zigness, Feb 24 2006
  

       Oh [zig] oh [zig]. Right, here we go then:
1)I didn't call for cheap cell phone detectors to be called magic. In fact, I explained how they work in a post about mid-way down.

2)This is the part you keep misunderstanding. Please pay attention because if you don't get it this time, I may have to break out the glove puppets. There is a difference between a device that actively solicits a signal from a phone and is able to identify said phone, (which is what is required to implement this idea) and a device that waits passively for a phone to send a signal. We've discussed the former to death, so I'm not going to bring that up again. The latter which you propose (three or more cell phone detectors with loop antennas and location determination done in software based from feedback) has several disadvantages that render it inappropriate for this scheme. Here they are:

1)Since your system is passive, you are dependent on the phone to send signals. It doesn't do this all the time, in fact it could potentially go for several minutes without sending a signal. Although you are correct in your assertion that your detectors will detect a phone in standby mode, it might take several minutes. This means that it's effectively invisible to your system until a signal is sent. Would this give a criminal enough time to burgle a house? Maybe, maybe not, but it's a troubling flaw.

2)The really big one. Your system has no way of distinguishing between phones. All it can do is say "here be phones" because it's measured RF energy. Let's say a phone sends a signal. This is detected by 2 of your cell detectors. How does each detector identify that this signal belongs to that phone, in order to perform location determination? It can't understand the signal so identification by ID is out. It is highly likely that each detector will be receiving different numbers of signals at any one time, so you can't reason along the lines that the signal closest to detector 1 must be the signal that was third furthest away from detector 2, because you have no way of knowing how the signal sets of each detector intersect, if they are intersecting. Even if all your detectors were receiving the same number of signals at any one time, you've no way of telling whether these signals correspond to a set of 10, 20, 30, 8, 7 or 26 phones. What this leaves you with is a system that can reliably tell you that there are cell phones in the surrounding area, and nothing more than that.

3)You have no way of delimiting RF energy, unless you're only going to sell to customers inhabiting bunkers. This means that not only will you not be able to identify phones or determine their locations, you won't even be able to say with any confidence whether they're on your property or whether they're on the other side of the street, in the neighbour's yard, passing by etc.

In conclusion your system cannot identify individual phones, because of this it cannot determine the location of any phone and it cannot be specific enough to inform the homeowner definitively of whether a phone is on or off their property. I'd say for a system aiming to automatically detect, ID and locate phones, this is a bit of a stinker.

Finally, did you have to stoop to the old "I'm exploring a patent in this area, so I'm not going to explain how this works, but I can do it honest!" hack? It's invariably the sign of someone out of their depth and trying to bluster their way out of an argument they have no hope of winning. I applaud your tenacity but in this case you are wrong wrong wrongety wrong.
DocBrown, Feb 24 2006
  

       Again, I would like to ask you to step away from the DIY-zone for a moment and consider a product to be developed by the telcos. It seems that this would be technically feasible. After all, the telcos will probably not mind losing burglars as customers, but would like to win customers owning real estate.   

       Perhaps the base stations on the premises need not have to function as the usual base stations. They just have to signal that they can sniff a phone. The existing base stations can then ask the identity of the phone and locate it.   

       The trick for such a service provider is to sign a deal with all telcos.
rrr, Feb 24 2006
  

       ////A cellular phone broadcasts information all the time// Yes but it's encrypted, so unless you have a very clever sniffer (please provide details) this wouldn't work....// Doc's anno on Feb 20, 2006.   

       //Since your system is passive, you are dependent on the phone to send signals. It doesn't do this all the time, in fact it could potentially go for several minutes without sending a signal.// Doc's anno on Feb 24, 2006.   

       Doc, you've hit an alarming level of arrogance and narrowmindedness on this one. A few days ago, you believed that phones send out signals all the time... then sometime later, it seemed that you believed they don't. That's not the sort of flip-flopping that I would expect from an "expert" on a particular technology.   

       The fact is that MOST phones, if in the on position, tend to send out a signal on the order of every few seconds. It depends on the mode that they are operating in. A passive detection system would work fine without your "several minutes" problem.   

       Also, there is absolutely no reason that the phones could not be "pinged". You just send a signal that mimics a base station, but I've already explained that.   

       Oh, and the patent I'm working on... this isn't place for that fight... my email is on my profile if you're compelled to pursue that line of discussion... suffice it to say that with your last post I've become personally offended, but I'm inviting your email queries.   

       Clearly, you're too thick headed to see anything beyond your pre-conceived notions about how all of this might (or might not work). Further, I think it's clear to anyone that has bothered (i.e. has too much time on their hands) to read all of this that your MFD was pre-mature and unwarranted. That's what all of this was about in the first place.   

       Also, I think it's interesting to note that you've position has gone from a tone of "It's magic! Won't work! No way! Not ever!" to one of "Ok... It might work a little... but... not very well!". Good grief man, this is the halfbakery. Most of the stuff on here won't work at all! This idea (while perhaps a little misguided) could actually be built and I couldn't give a hoot if it's perfect or not.   

       You've been on here long enough to know that.   

       I used to teach at a private university (courses such as Aircraft Engines and Systems, Advanced Aircraft Performance, Navigation, and Aviation Electronics), and I remember having a student just like you. No amount of pointing to paragraphs or providing additional materials or anything would convince her that a particular piece of avionics worked the way that it did -- it just "didn't make sense" to her. (It was the VOR receiver she was having trouble with for those that are curious).   

       As I learned then, there comes a point where you just throw up your hands, grade the test, and move on.
zigness, Feb 24 2006
  

       A wee note about the phone detector that you've linked to, [zig]:
i) It doesn't say anywhere that the device can identify individual phones nor send messages.
ii) It says clearly that the device only listens and does not transmit. The warning it gives may either be via red light or an audible message.
Jinbish, Feb 24 2006
  

       My mistake... edit made... I'll look for a link to show where that one came from.
zigness, Feb 24 2006
  

       [zigness], this is a debate about cell phone signals. If there was anything more trivial to be getting worked up about, I'd be surprised. This has been a lively and thought provoking discussion. One of the best that the halfbakery has seen in quite a while. There is no need for this to become personal.   

       The same goes to you [DocBrown], you've debated marvellously up until this point but the last paragraph of your last annotation was completely unnecessary.
hidden truths, Feb 24 2006
  

       [Zig], congratulations, you've spotted a minor inconsistency in my argument. The first statement of mine you quoted should not have tacitly conceded that phones transmit all the time , but should have noted that they transmit frequently but not constantly. As to your other points:

- You're correct that phones could be pinged, but to do that across all networks and determine location, you'd need 3 antennas per network. We've discussed this one to death.

-You state //If you actually looked at the link I put up and READ anything about it, you would have realized that this $595 detector can send a message to the offending phone. Guess what? It CAN identify the individual phone!//. Have a look at this direct quote from the link:
"The CellBuster, when turned on, will continuously monitor for radio waves emitted from wireless communication devices. The device doesn't transmit and only receives signals".
In other words, as [Jinbish] has realised, it can't ping phones and it can't ID an individual phone. Since it can't detect individual phones, location determination is impossible. Impressive that you've gotten so desparate to prove me wrong that you've actually stooped to trying to invent new powers for an existing product.

//Clearly, you're too thick headed to see anything beyond your pre-conceived notions about how all of this might (or might not work).//Right back at you pal, but I think I'm a bit more entitled to my pre-conceived notions, since they're based on how this technology actually works.

- My magic MFD is not unreasonable, given that your best efforts to date have rendered a design that would allow detection of radio frequency activity in the cellular band in the surrounding area. No IDing of phones, no locating of phones. In fact, your amendment might as well be MFD redundant, since it doesn't add anything that's not available on the market now - the proof is in your own link.

- I'm trying very hard to stay civil but your patronising tone //I used to have a student just like you// etc is starting to bug me. I'm not your student, and however much you'd like to believe you have a superior knowledge of this technology is just isn't the case, as evidenced by your child-like arguments:
// //Your system has no way of distinguishing between phones// Nonsense. //
Look back over the annos and see who's been responding quoting standards and actual technological details and who's been dug in with his head in the sand repeating variations on the phrase: "of course it'll work, they're only radios". You're more like your former student than I am.

I urge you to go read some more about this and come back when you understand how phones work, either that or shut up, but please don't try and tell me you know better than me, because you clearly don't. Has the thought crossed your mind that the reason I'm being so stubborn about this might just be because I'm right?
DocBrown, Feb 24 2006
  

       But can you move a fishbowl with it?
calum, Feb 24 2006
  

       Yes, but not a specific fishbowl. And you can't tell where it is either.
DocBrown, Feb 24 2006
  

       //Yes, but not a specific fishbowl. And you can't tell where it is either.//   

       Schrodinger's Fishbowl??
Jinbish, Feb 24 2006
  

       I've just added another link with some relevant information... unfortunately, no mention of fishbowls.
zigness, Feb 24 2006
  

       //Schrodinger's Fishbowl// Nope, Heisenburg's. Maybe.
coprocephalous, Feb 24 2006
  

       //Nope, Heisenburg's. Maybe.//   

       I was going to say that - but wasn't sure...
Jinbish, Feb 24 2006
  

       Doc, I'm closing my arguments with this:   

       "Cell phones poll the cellular base station with the strongest signal every few seconds." (That's from the link I just put up since I knew you'd need some reliable 3rd party source.)   

       If that statement is true, then I absolutely can detect and track a particular phone simply by monitoring it's progress as it moves through an area, and I don't need to do anything special. If it's rate of transmission is too small for that, I can simply ping it as needed (as you finally agreed is possible).   

       //My magic MFD is not unreasonable, given that your best efforts to date have rendered a design that would allow detection of radio frequency activity in the cellular band in the surrounding area. No IDing of phones, no locating of phones.//   

       Then you haven't been paying attention.   

       Your insistence that they can't be tracked flies in the face of existing (and old) technology for radio location devices. Simple loop antennaes do the trick. (I'm beginning to think that you might not know what those are). It's the same way that they track bears in the wild that have been fitted with radio collars. Any radio signal can be located on a grid using this kind of thing.   

       As I re-read everything here, it occured to me that the main thrust of your argument is that you would be forced to work within the protocols and cell standards of the system, and I see a different way.   

       Call me wrong all you want. I'm content in the knowledge that I could actually build one of these using one of a few possible methods, and on that basis alone I still disagree with the appropriateness of your MFD. (Which, after all is what started all of this).   

       It's been interesting -- and fun -- but I've said all I'm going to say about it. You're invited to email if something's still stuck in your craw.   

       And, no I'm not going to address the fishbowl issue. :)
zigness, Feb 24 2006
  

       "I'm closing my arguments"   

       As if!
DrCurry, Feb 24 2006
  

       LOL! All I can do is "try". :)
zigness, Feb 24 2006
  

       I think [Doc] conclusively proved to me that you can't get an incoming cell calls, since you can't find the phone. This explains why my daughter won't ever pick up the phone, and uses it only as a dial out device. :)   

       In all seriousness, I think the argument is over "magic". I don't share [zigness] enthusiasm that this is all that easy to build. Having said that, given that it is a radio, and we're not talking about using nano, vacuum energy, or anything of the sort, one would have to assume that it is buildable at some level of effort, probably approximating the level of effort already put into these arguments.
theircompetitor, Feb 24 2006
  

       // "Cell phones poll the cellular base station with the strongest signal every few seconds." (That's from the link I just put up since I knew you'd need some reliable 3rd party source.)

If that statement is true, then I absolutely can detect and track a particular phone simply by monitoring it's progress as it moves through an area, and I don't need to do anything special. If it's rate of transmission is too small for that, I can simply ping it as needed (as you finally agreed is possible).//

I'm glad you're going to close your argument there, because it makes it very easy for me to win. As I've acknowledged (not "finally", but since waaaay back up there) you could ping a phone, and you could possibly locate a phone but to do this you would need 3 basestations per network. You could not use the system you proposed a few annos back (Remember? The passive system that you insisted -in contradiction to the company's own marketing-was capable of transmitting a ping and IDing phones?) because that could not identify which signal belongs to which phone and since it can't do that it couldn't locate any phones, and it can't track the movement of phones because your software, however wonderful couldn't correlate any of the data.

I'm not arguing that bears can't be tracked in the wild using radio, but that's not quite the same as saying that cell phones can be tracked in precisely the same manner. When was the last time you saw a mobile phone on a bear's tracking collar? You're welcome to suspect I don't know anything about loop antennas, I in turn suspect that you possess a rudimentary understanding of radio technology (square peg) which you'd really like to translate into a mastery of modern telecomms (round hole). It's not happening.

You've correctly identified that my main objection to this idea is that it isn't implementable with the standards existing today. This doesn't make me stuck in my ways and you a radical genius it just means that one of us recognizes that there's no point in thinking out of the box when the box is all there is! I don't rule out the possibility of such systems coming online in the future (indeed, the E911 stuff means that good ol' Uncle Sam will be keeping a close eye on you in future), nor do I believe that this is an impossible product to make as the field of telecommunications advances. But what I do say is, under current standards, as it reads, the idea demands that existing technology do something it ain't capable of doing. What do we call this phenomenon? Magic!
DocBrown, Feb 24 2006
  

       Doc, re-read my last anno... especially the part about loop antennaes. Did you somehow miss that? Do you know what I'm talking about? Do you know what they are?   

       I really am not planning on offering anything new to this one, just a referral back to my "closing argument".
zigness, Feb 24 2006
  

       I read your last anno. very carefully [zig]. My understanding of loop antennas is limited but I believe you'd be seeking to utilize the fact that loop antenna signal strength peaks in the plane of the loop with strong nulls in the perpendicular axis. So far, so not very useful if you're tracking multiple signals across multiple antennas and you have no method of differentiation.

I'm going to choose to read your silence(particularly on points like your puzzling lying about the capabilities of the passive detector you linked to, and your refusal to acknowledge the non-ability of your system to locate or ID phones) as tacit confirmation that you have no valid argument to offer, and your continued references to loop antennas as a rather pitiful attempt to drag the argument to somewhere you might be able to claim superior knowledge. I'll freely admit to having lots of learning left to do in every field, but I know phones better than you do, and I think it shows.
DocBrown, Feb 24 2006
  

       You know what, this brings back fond memories of the great coffee-colored coffee mug debate. ("I'm right, you're wrong!" "I'm right, you're wrong!" "I'm right, you're wrong!" "I'm right, you're wrong!" "I'm right, you're wrong!" "I'm right, you're wrong!" and so on.)
DrCurry, Feb 24 2006
  

       I don't know if I can agree with that [DrCurry].
theircompetitor, Feb 24 2006
  

       [Doc], in terms of you making this statement about me: //your puzzling lying// -- I SAID "My mistake... edit made... " in an anno that followed my error immediately (within a few minutes) once I realize that I had mixed up something I read on the site with something I read somewhere else -- not related to that product. That was an error that I quickly and freely admitted to, and I subsequently changed the anno. If you're going to get that insulting, at least get your facts straight.   

       Your personal assaults notwithstanding -- I really don't care what you THINK I know -- I've explained my technical points.   

       A phone transmits a radio signal every few seconds that can be detected, triangulated, and tracked without ever having to be "decoded" in the system. The "identification" results from knowing where it is compared to knowing where all of the other ones are. (A computer is pretty good at remembering stuff.) That sums up my point, and your belief otherwise doesn't change the reality of whether it will work or not.   

       I don't see the point in more technical arguing. My original attempt was to show that "magic" was not required to make this work out, and I stand by that.   

       You're not changing your position, I'm not changing mine. That's fine. Call me names. Call me wrong. I really don't care. I've got to go back to making a living for today. (I don't recall ever seeing a reference to the HB on one of my bank statements). There really just isn't anything more to be gained with this one.
zigness, Feb 24 2006
  

       [zig], I apologise, I missed your amendment referring to the detectors. I also apologise for my ill-considered personal remarks - my temper is a failing which sometimes gets the better of me.

For the rest of it, I must agree that we appear to be at impasse. I cannot understand how you think it will be possible to identify a particular phone's signal, given that it arrives at different antennas at different times and given that it is indistinguishable (to your passive detectors) from the signals of other phones that may be transmitting simultaneously in the same area, and thus also be being received by your antennas. That's the crux of the matter because without the capability to ID and thus track phones, all such a system could do is to say that phones are active in a not very sharply defined area.

I share your feeling that there's not too much benefit to be gained from carrying on. For my part I've enjoyed the debate. Happy weekend all, I'm going home.
DocBrown, Feb 24 2006
  

       I too have enjoyed it.. quite a lot. Have a good weekend, [Doc].
zigness, Feb 24 2006
  

       Should I now conclude that cooperation from the telcos is 'magic'? I understood that you can shout it when an idea changes laws of physics. Which excludes the behaviour of telcos, doesn't it?   

       From the interesting discussion between the experts I got the impression that you can make this work if the telcos want it...
rrr, Feb 26 2006
  

       To succinctly summarise the above:
i) you can use passive antennae to triangulate a radio (phone) signal
ii) It can be potentially very difficult to distinguish one radio signal from many, and to identify it's location (based on signal strength alone)
iii) If you know the correct code to transmit (mimicking a base station), a phone will reply "Hello, I'm here".
  

       So yes, this is possible with telcos agreemtent. It is also theoretically possible without - although improbable.
Jinbish, Feb 26 2006
  

       It might be possible [Jin]. Problems you would encounter:
1)To provide the level of location detail required, you'd have to have one cell per house. That's way over capacity for your typical suburban environment and completely impractical in more built up areas (eg. block of flats) unless you rebuilt the block in such a way that RF energy couldn't pass between flats. Assuming you operate in the suburbs and the cost of the cell was met by the consumer (expensive but not unfeasible) you'd then run up against problem....
2)RF leakage. Even with one cell per plot, it would be very hard to prevent phones in the neighbour's yard signing on to your cell, which would give a false positive. Or a phone which passed by your house from signing on, again an FP. Or a phone that was on your property, then moved next door but stayed on your cell. It could be done, but it would require sealing of your plot against RF. This would have pretty harsh effects on your radio and aerial-based TV reception, not to mention put a bit of a downer on you when you look out the window. Assuming you made these sacrifices, you've then got a system that will reliably tell you that a phone's on your property, but not precisely where it is. Having gone this far, you could then add another 2 cells on your plot for the purposes of precise geolocation!

I guess the summary is that the MFD magic was inaccurate, but that this would be a colossal pain in the butt to implement, involving compromises few consumers would be likely to make. That's my take anyway. [zig] is confident that there's another way to do it, maybe he'd post a synopsis of his thoughts if you ask nicely.
DocBrown, Feb 27 2006
  

       not a bad idea. but needs some modifications.
mobdir, May 06 2007
  

       //Tell or text// sp: teletext
BunsenHoneydew, Jul 07 2007
  
      
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