Disrupting Inductive Neck Loop Earpiece with EMP?  - Page 1
Forum section: electronics / projects

author: Shidoshi
author_rank: Contributor
timestamp: November 13, 2010, 06:23:49 pm
content: I have currently made a small handheld EMP device originally from a 9V battery which later got converted into 8x9V batteries which was outputting 52.5V and down to 45V after a half hour or so, 500mAh batteries **** big time, will go on to 3000mAh once I figure out all the kinks in the current design though.The reason for creating this small EMP is to block out the inductive neck loop system which students are using to cheat on their exams, they use an MP3 player and a wireless earpiece which captures the magnetic resonance at about 300Hz - 5300Hz, some even go to 8500Hz. Since I wasn't able to replicate this low output, I tried the EMP method.The pulse works fantastically at around 1m range with some grounding issues however, the original design was only intended as a demo and at the original 9V nothing happened with the increase of power I managed to get the multimeter to show me 200V output from 8x9V batteries lol. At about 1m range the earpiece picks up the EMP as do 3V pc speakers, I need the pulse to be received in a 10x10m room though.I was also thinking of digging up an ancient HAM schematic to output somewhere near the magnetic resonance the earpiece works on, if HAM and submarines can do it why can't we?I'm seriously stumped as to what the best option for our centre is, one more point, it is important that the device can run on a small current, well actually, should be covert, able to be mobile, say in a backpack with a few 9V batteries or other power source that is small enough to conceive in a bag.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: November 13, 2010, 06:48:20 pm
content: It would be a hell of a lot easier to detect their transmitter, and expel them from school.

author: allanw
author_rank: Frequent Contributor
timestamp: November 13, 2010, 06:56:27 pm
content: Wait, why can't you notice them using an earbud?

author: Shidoshi
author_rank: Contributor
timestamp: November 13, 2010, 07:05:59 pm
content: to JohnS_AZ:1 device that can block a whole room from current and future attempts to cheat on tests or extra staff to strip search each individual student and violating their rights... I think the cheaper and easier method is to not encourage students to try and cheat and not get caught but to study and pass their exams on their own and in turn raise the school's standards.Some educational institutions have staff that take money from students to mark them as present and give them a solid report, a recent TV report on some New Zealand universities demonstrated this.Just attempting to stay one step ahead. Of course if anyone is caught we will try to expel, however expulsion not every time works in our favor, there are many variables to take into consideration.to allanw:Magnetic resonance, some devices can be as small as 3mm in diameter and so far down the ear canal that they can't be seen without probing something down their ears.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: November 13, 2010, 07:11:36 pm
content: Okay. I don't know a thing about these inductive neck loop things. Can you point to a web page that talks about the technology?The point: Figure out what the transmitter is doing, and build a bigger,more powerful one. Maybe blast them with Neil Sedaka songs from the 70's.

author: Fraser
author_rank: Super Contributor
timestamp: November 13, 2010, 07:11:47 pm
content: Shidoshi,When I first saw your message I was thinking 'what the heck !' but having seen your reason I understand your drive behind this project.I have used what could be termed EMP emitters in my work life but they use much higher powers than you are talking about here and are not exactly portable ! They would also damage anything electronic within 10m so aren't really appropriateYou have not detailed your circuit so I have no idea what you are using in terms of a pulse generator or power amplifier stage. Any decent EMP device with any sort of effective range will need a significant ERP and the pulse repetition frequency (PRF) will have a significant effect on average current consumption.My usage of EMP was to disrupt or damage electronic semiconductor junctions, yours is really more of a jamming application which is somewhat different. In the Cold War days the 'Woodpecker' could often be heard as it stepped through the HF spectrum. I once listened to that signal moving up from around 2MHz to over 30MHz knocking out thesignal on each of my fifteen HF receivers as it did so...... it was capable of completely disrupting my comms links while it was present. I would suggest you consider building a mini 'woodpecker' by feeding a swept pulse oscillator into a reasonably powerful RF power amplifier that feeds an inductive loop around the exam room. The swept frequency should be at a reasonably slow rate in order to create a intermittent jamming signal that covers all frequencies between 300 Hz and 10kHz. The less spectrum friendly option would be to build a spark gap transmitter as that would produce broad spectrum RFI. One can easily be built using a simple 555 oscillator driving a car ignition coil with the EHT jumping a 5mm spark gap and feeding a long piece of wire or large loop.... a most unpleasant experience for anyone receiving it on an earpiece !Now the legal bit…. Making a powerful EMP device or jammer of any description may be deemed unlawful in many countries and is definitely so in the United Kingdom. You always have to consider the effect the EMP device or jammer will have upon legitimate users of the RF spectrum. Broad band RFI producers can be a very anti-social act. Consider legitimate hearing aid users.Your establishment should carefully consider it’s legal position and should also consider stopping the problem in a simpler manner. If the technique of using an inductive earpiece is known, the students may either be searched on entry or regular checks on their ears made. The only hearing aids fitted should be to those with a medical condition. The KISS principle applies !I will not provide the circuit details needed for an EMP device or a jammer as they are freely available on the NET and personally I do not wish to be associated with such a device in a civilian environment.

author: Shidoshi
author_rank: Contributor
timestamp: November 13, 2010, 07:35:08 pm
content: Transmitter/Receiver specs:http://www.ioffer.com/i/spy-micro-invisible-earpiece-wireless-earphone-cheat-143294781?source=eisiEMP Schematics:http://www.freeinfosociety.com/electronics/schemview.php?id=2279(REV.01)Students with hearings-aids or pacemakers are segregated. Building the Woodpecker and feeding a pulse through an inductive loop around the room won't only be concentrated within the 10m2 room but will also spread in every other direction too, right? Since a parabola wouldn't be feasable, I think that even though this is a great suggestion, I would like to hear some more suggestions before thinking seriously about your method, Aurora. Ahh, also the spark gap method is rather noisy, is it not?

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: November 13, 2010, 07:39:39 pm
content: I still don't understand. What is actually transmitting the signal that these earbuds receive?

author: Shidoshi
author_rank: Contributor
timestamp: November 13, 2010, 07:42:33 pm
content: Speaking of cold war, what are your thoughts on a ELF/ULF/VLF transmitter? Been trying to figure out how the Russians used ZEVS in submarines and to replicate that method somehow or if feasable at all outside of water...The signal is on a neck loop system using magnetic resonance. The inductive loop system uses a magnetic pulse to transmit VLF magnetic vibrations. The earpiece picks up the magnetic resonance at a short range and using a miniature speaker/magnet converts the magnetism to audio. Very similar way normal speakers work but on a much lower frequency range.

author: Shidoshi
author_rank: Contributor
timestamp: November 13, 2010, 07:46:05 pm
content: Some of these manufacturers state that this system is un-jammable, in theory this is not true. We beleive that nobody has gone public with their methods yet

author: .o:0|O|0:o.
author_rank: Regular Contributor
timestamp: November 13, 2010, 07:52:10 pm
content: Quote from: Shidoshi on November 13, 2010, 06:23:49 pmReally? Why?

author: Shidoshi
author_rank: Contributor
timestamp: November 13, 2010, 08:01:33 pm
content: Some examinations are conducted outside of a classroom environment.

author: Fraser
author_rank: Super Contributor
timestamp: November 13, 2010, 08:14:48 pm
content: Shidoshi,Nothing is unjammableI have had a think about your situation over my dinner. I am an RF tech so magnetic loop links are not my speciality. I don’t think my idea of a swept pulse oscillator is going to be that effective in your very low frequency application.From what I know of the system you are up against, it does not use a modulated carrier and is basically audio being fed into a loop at a high enough level to reach an inductive pickup in the earpiece, I presume the inductive pickup feeds a high gain audio amplifier. This is using the basic principle of close proximity inductive coupling, so to disrupt it you would need to generate an intense magnetic field that is actually a single frequency of say 1kHz. The earpiece inductive pickup would detect that field and reproduce an annoying 1kHz tone in the users earYou have two obstacles..... near field versus far field flux density and the challenge of driving a very low impedance loop with an audio frequency power amplifier. The manufacturers of hearing aid loops know how to deal with these challenges but I regret I do not. You could consider speaking to a hearing aid inductive loop vendor and establishing whether one could be used as a jammer by feeding in a 1KHz oscillator tone which the unit would radiate into the room.Another approach is the BLACK BOX Hoax ! Construct a black box and fit some fancy digital meter to it with a bright flashing LED, then advise all students that an inductive earpiece detector will be deployed in the room. Anyone found cheating will be dealt with harshly. Bluff will sometimes work.

author: Shidoshi
author_rank: Contributor
timestamp: November 13, 2010, 08:27:15 pm
content: HAHAHAHAHA nice one! That is pretty fun until it's discovered to be a hoax!Yes, it does contain a high gain amplifier indeed.1Khz sounds right on, I had that thought last night but my mind ventured elsewhere. I never thought of the possible obstacles however. Great participation on your behalf Aurora, much appreciated!I will speak with some manufacturers right away, thank you for the heads up on that!Will post any obstacles/progress on here as soon as I know of anything new!By the way, you don't happen to have a handy working schematic for a 1Khz transmitter would you? Mr. Google will be happy to comply if you don't, I can only assume

author: Fraser
author_rank: Super Contributor
timestamp: November 13, 2010, 08:51:46 pm
content: Shidoshi,1 kHz transmitter....Hmmmm that is a bit of a challenge ! I suppose the audio amplifier could be considered a 'transmitter' but a pretty unconventional one ! What you will need is a single loop around an area driven by a powerful Audio Frequency amplifier that does not mind feeding what is effectively an extremely low impedance at audio frequencies. Some clever loop drive circuitry will be required and I regret that I do not have that knowledge and Google seems very quiet on the schematics side of hearing aid loop drivers.I thought about using a standard reasonably high powered audio amplifier feeding into some form of step down impedance transformer but I do not know of one that will step 4 Ohms down to milliohms. If you connect a loop directly to the amplifier output I suspect you will quickly overheat the PA stage and kill it just as may occur with a shorted loudspeaker.I think you will need to do some hard Googling on driving very low impedances at audio frequencies. There are many manufacturers of the loop amplifiers but very little detail of what they contain in terms of design.The 1kHz tone may be produced using a simple 555 circuit in astable mode.... if you use a square wave it will produce quite a distorted sound ....... it would be like a loud mosquito in their earOn a side note.... If you are successful in your desire to deploy a countermeasure against cheats, imagine what will happen when you first switch it on.... you will hopefully see all the cheats with pained expressions on their faces as a solid 1kHz tone drills into their earThey will want that earbud out of their ear canal pretty quickly or else suffer considerable discomfort and distraction during the exam

author: cybergibbons
author_rank: Frequent Contributor
timestamp: November 13, 2010, 09:16:35 pm
content: I don't understand why people would go to such lengths to cheat... but anyway.These are just the same as inductive loop hearing aids in use everywhere in the UK. I've set up quite a few temporary induction loop systems using hired kits, and it's very easy. If you aren't worried about sound quality, an audio amp connected to a long length of mains flex will do the job. Connect to a signal generator doing pulses of 1kHz at extremely high level, and you'll quickly find the students cheating - they'll be the ones ripping the earpieces out of the side of their heads.Just be warned, anyone with hearing problems and using a hearing aid will experience the same.

author: tyblu
author_rank: Frequent Contributor
timestamp: November 13, 2010, 09:25:57 pm
content: This is fascinating - I didn't know these earbuds existed. Was actually interested in making something similar for my final school project, last year. Looking online yields versions with receiver and power circuitry stuffed into a AAA battery-sized package, connected to the ear bud. This will only get smaller, 'til it fits in your ear like a hearing aide - in fact, this probably already exists as it was the size I was going for in the project.If I were in your shoes, I would consider multiple smaller-range devices, such as what you have, to ensure you stay below certain SAR measurements and be able to selectively turn off the jamming signal near some individuals whose electronics are of vital importance (pace makers, and whatever other gadgets we'll be using in the few years to come).Good luck! Would love to hear more about this.

author: cybergibbons
author_rank: Frequent Contributor
timestamp: November 13, 2010, 09:26:16 pm
content: The proper kits are current mode amps rather than voltage mode. A good audio amp can drive very low impedances, and a long length of flex is easy enough - buy a 100m length of 0.5mm2.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 13, 2010, 10:30:59 pm
content: Remove the whole motivation to cheat. Allow them to have some references (notes or even a textbook) and design the exam to be based on applying the knowledge. It's pointless to make them remember reference materials - they'll remember it after lots of use - so have them learn how to actually solve problems. In the end, they'll forget the stuff that doesn't count and remember the stuff that does.

author: .o:0|O|0:o.
author_rank: Regular Contributor
timestamp: November 13, 2010, 10:58:19 pm
content: Quote from: NiHaoMike on November 13, 2010, 10:30:59 pmIn some countries they complement written examinations with oral examinations, where you are expected to solve a problem on a blackboard in front of a board of examiners, while explaining your steps as you proceed... None of this multiple choice* "who wants to be a millionaire" nonsense - the real world doesn't work like that ....but you can automate the marking process and save money that way..o:0|O|0:o.

author: marianoapp
author_rank: Regular Contributor
timestamp: November 14, 2010, 12:31:08 am
content: you could also buy your own earpiece and walk among the students while they are answering the test.. as soon as you start receiving something you'll know how the cheater is

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 14, 2010, 02:56:09 am
content: Quote from: .o:0|O|0:o. on November 13, 2010, 10:58:19 pmAt my university, multiple choice exams are very uncommon for the higher level classes and just about all the exams either allow "bring your own references" or supply some sort of reference sheet. What I like the most are "practical exams", where the whole objective is to either fix something that doesn't work properly or create something using the supplied materials. Basically a good simulation of a real world situation.

author: Shidoshi
author_rank: Contributor
timestamp: November 14, 2010, 04:12:06 am
content: QuoteSome devices transmit up to 10cm, that would be an uncomfortable moment for both parties. The longest ranged devices state they can transmit 70-100cm which would mean the source could come from the pocket rather then a neck loop system, either way there would be certain uncertainty, also the system can be triggered on/off by the operator via a switch as soon as someone approaches.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 14, 2010, 05:20:05 am
content: They'll just find some other way to cheat. But if you allow use of reference materials and redesign the exam to account for that, clever tricks to hide information would not offer much advantage if any. (You'll still need to prevent unauthorized sharing of answers but making different versions of the exams would make that useless. Maybe even make subtle changes that cheaters probably would not notice but would greatly change the answer.) In other words, to quote Dr. Ehsani (a power electronics professor at Texas A&M), "Make cheating obsolete."

author: Bored@Work
author_rank: Super Contributor
timestamp: November 14, 2010, 10:07:00 am
content: If they can cheat with an MP3 player, then I would also say the exam questions are asked the wrong way. It sounds they are parroting exams. Exams where it is just checked if people can repeat what they have memorized, like a parrot, instead of checking if they understood the subject.But anyhow, if you roughly know the frequency these devices use, build a receiver. You don't have to decode the signal, just detect its presence. You will need something like a (hand-held) loop antenna (loop antenna, because of the low frequency). A cap in parallel with the loop antenna to get a resonance frequency in that kHz area you are interested in. Then an audio pre-amplifier (simple two-stage transistor or the like). And then you can rectify the output to display signal strength on some meter.

author: Frenchie
author_rank: Regular Contributor
timestamp: November 14, 2010, 11:05:35 am
content: Quote from: NiHaoMike on November 13, 2010, 10:30:59 pmI agree! Open book exams are both a blessing and a curse, even though you have the information, take too much and you'll spend the entire exam looking for what you need. My first ever open book exam I didn't bother studying and ended up only just passing. I learnt pretty quickly after that, having the material on hand is one thing, knowing how and when to use it is another entirely. There's no point trying to read 3 chapters of a text book in a 3 hour exam as you need the time to solve the questions.These days if I have to remember something non-trivial from my earlier years of university I have to look it up in a book. In that regard, teaching students how to quickly find the information they want and then apply it correctly is invaluable. I suspect in most cases, students cram in a semester's worth of learning and then promptly forget most of the finer details when they go on to learn something else the next semester.All that said, I wish the OP well in his efforts to crack down on high tech cheating, it's rather a neat idea!Of course, all of the above is moot if you use exam problems straight from lectures, tutorials or the textbook - quite a few lecturers haven't worked that one out with OB exams.

author: Shidoshi
author_rank: Contributor
timestamp: November 14, 2010, 04:04:04 pm
content: QuoteWe're trying to stay one step ahead.QuoteYes, some exams are required to establish that the participant recognizes the meanings of symbols and can distinguish minute differences in wording.QuoteOur aim isn't to humiliate and punish individuals at this stage but to just make the current process impossible to work without openly discovering what counter-measures are in place, ignorance is bliss.QuoteNot all situations derived from the exam subject(s) are a future reference material instances, some material is required for the students to know instinctively.We appreciate the discussion of semantics, detouring/deferring from the current task does bring some ideas to the table that would otherwise be ignored, however we are adamant to get this Project/Design to work as intended, we have pretty much openly discussed all methods here pointed out and do think that the objective set out on the first post is the most feasable solution for the current instance without directly affecting any third parties in a demeaning manner.I personally appreciate all of your feedback. My thanks.

author: Bored@Work
author_rank: Super Contributor
timestamp: November 15, 2010, 07:26:46 am
content: Quote from: Shidoshi on November 14, 2010, 04:04:04 pmYou are talking bullshit. The "solution" is neither easily feasible nor safe.If you manage to send out your pulse you severely endanger the hearing of those wearing the receivers. The same applies to those wearing hearing aides and pace makers. Even if you send out much lower energy you are still risking this. You also have very little control about the range.And, assuming you manage to create your stupid pulse, do you have the funds to compensate not only the people you hurt, but also all people for all the other damage to electronics it will do? E.g. killing people's digital watches, cell phones, labtops, iPads, their normal MP3 players, their car keys, their credit card? And is your uni willing to re-equip the lecture room every time you send out you pulse, after you killed equipment like projectors, the loudspeaker system, lights dimmer?So, whoever you are, whoever you discussed this with, you sound more like a bunch of shitheads without a clue, wanking about something they don't understand (liberal arts students, eh?) than responsible electrical engineers.

author: Fraser
author_rank: Super Contributor
timestamp: November 15, 2010, 09:14:28 am
content: BoredatworkThanks for the input.My first response to the OP stated the legality issues and I trust Shidoshi has taken them on board.Let us all be really clear on one point though.... the term EMP is emotive and we are not talking about EMP field densities here that disrupt and damage semiconductor junctions in the 'far-field'. That is a topic with which I am very familiar and Shidoshi has neither the design nor technical resources for such a device. I should also warn that a true 'far-field' high power disruptive or damage capable EMP emitter could be considered by the authorities to be a terrorist tool so it's not something to be played with.Your comments on disruption to Pacemakers is well made. Modern Pacemakers use an inductive coupling loop for communication with the programming computer. The thought of exposing such a delicate device to any form of disruptive EM field sends a shiver down my spine ! It's a definite no-no and who is to say that a person fitted with a Pacemaker would not be effected by simply walking past the room that has the EM device deployed.Your comments regarding the acoustic risk to the earbud user are significant. No one would be permitted to produce a device that has any potential to harm a student. A full technical risk assessment would be required and the likely outcome would be that it is not predictable or safe to use.I come back to my proposal. Purchase a commercial APPROVED hearing aid loop system and inject a 1kHz tone into the input,. The ALC will compress the tone to a safe level but will cause an annoying tone in the earpiece of the person using an inductive earbud. The risk here would be the quality (or not) of the earbud receiver. If it is poorly designed it may be able to produce harmful levels of audio even when stimulated by an approved audio loop system. As the loop system would be an approved design this could lead to a complex legal argument as it is the receiver that is theoretically at fault but Shidoshi is deploying the loop system as a countermeasure and not for it’s intended purpose. For this reason I agree that this whole path of causing interference to the receiving earbud is a poor strategy and as I said in my first post…. Consider other options and apply the KISS principle.Shidoshi - Why are MP3 players allowed in exams? Use a standard security metal detector wand to find the MP3 player and associated inductive loop driver and prevent cheating that way. I believe schools already do this in some parts of the world to detect knives. Normal precautions for Pacemaker wearers apply.

author: .o:0|O|0:o.
author_rank: Regular Contributor
timestamp: November 15, 2010, 04:05:23 pm
content: Quote from: .o:0|O|0:o. on November 13, 2010, 07:52:10 pmWhy should it be "covert"?.o:0|O|0:o.

author: .o:0|O|0:o.
author_rank: Regular Contributor
timestamp: November 15, 2010, 04:14:17 pm
content: Quote from: Aurora on November 15, 2010, 09:14:28 amWhat about lower powered disrupters covertly and strategically misplaced in rucksacks then....o:0|O|0:o.

author: Time
author_rank: Frequent Contributor
timestamp: November 15, 2010, 05:42:50 pm
content: I think this is more of a jamming concept than a destructive EMP concept. There is no way you can produce electric field levels large enough with a power fet and 555 timer to physically cook electronics. I have played around with blasting 5 megawatts of microwave power at various pieces of electronics and even than destruction could be hit or miss depending on shielding and orientation in the field. I have lost quite a few garage door remotes and digital watches to HPM pulses.You are better off just broadcasting something stronger in the same spectrum as their ear pieces, continuously- as John suggested. EMP is a pretty a dumb and nonsensical approach to this. Your low range proof of concept is invalid if you are trying to meet a power density requirement due to small space constraints. Your electric field loses go with the inverse of the distance squared so to scale from 1 m to 10 m will require quite a significant increase in power/energy density in your base system.Use a pulsed spark discharge of about a 1/2 inch to create intense EMI in the area.This will produce a noisey as all friggin hell environment. Aside from possibly reseting firmware, nothing will be bricked though. Pacemakers are usually pretty EMI hardened and won't be effected by something like this. Cell phones as well but anything with a low frequency antenna will suffer. Not to mention the audible noise its going to make. It will sound like something right out of Teslas lab. Systems like this will effect a huge area but any amount of shielding will stop them.Something like this is what you need if you can't get over the caveman approach of blasting emp through the air. This is a realtively simple solution but it would probably cost 1000 USD initially and if you make mistakes it will cost more. Consider other options.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: November 15, 2010, 06:48:36 pm
content: You know, you can call me another paranoid American if you like, I really don't care, but I feel compelled to say that this thread has made me uncomfortable, which is why I stopped participating a few days ago.- If the goal was to catch cheaters, you wouldn't try to jam the signals or destroy anything through EMP, you would build a small receiver to detect the cheaters and deal with them appropriately.- If the goal was to stop cheaters, you wouldn't build the jammer into a backpack, you'd put it in a big shiny box on the wall with a flashing red light and tell EVERYONE ABOUT it.- Who -DOES- use loop technology legitimately? Mass transit facilities, museums, theaters, hospitals, schools, the Secret service and other law enforcement folks...You guys do what you will. Count me out.

author: Shidoshi
author_rank: Contributor
timestamp: November 16, 2010, 02:27:19 am
content: QuoteFirst few posts:"Students with hearings-aids or pacemakers are segregated."QuoteElectronic equipment is strictly forbidden in exam rooms, everyone knows the rules before going in, even if we had 1 million dollars or so to spare on generating an explosive EMP blast to be anywhere near powerful enough to remotely reach the level of EM required to collaterally damage any equipment unintentionally, yes, we would be technically held accounted for that.QuoteApologies for the "covert" request, after having the EMP image from Ocean's Eleven in my mind, I was aiming to get the opposite of 'gigantic' and accidentally over stated the dimensions required. Looking for small and somewhat reasonable dimensions to still be classed as 'portable'.QuoteGSM jammers anyone? GPS jammers? Used by car thieves to jam the satelite tracking system for stolen vehicles, yet, readily available to anyone even if not in law-enforcement.QuoteThank you for this. Have been heavily considering this option and transmitting over 1-1.5Khz.QuoteExactly, that's very true. Cheating on exams isn't legitimate, but preventing such occurances withing the extent of the law, taking the human condition into consideration is perfectly legitimate.QuoteWe have a jammer which ranges from 80Mhz to 3.2Ghz if I'm not mistaken, the configuration isn't superb but is working, power consumption is awful, it's turned on at the mains often and barely visible on the wall-mounted setup. We have a portable one also with a much reduced range but works like a charm for the desired application.EVERYONE here has contributed greatly towards the cause, even as negative as some comments might have sounded.Thanks all, very much appreciated.

author: Shidoshi
author_rank: Contributor
timestamp: November 16, 2010, 02:35:57 am
content: Quote6 years ago when the first GSM jammer was introduced, everyone wanted to see their phone being jammed apparently, and due to a few experiences, we've widened the range on the system used greatly.The first system jammed the pilot signal, so if someone came in with an existing call, the call wouldn't be affected, within a few days we managed to jam both pilot and carrier. Biggest issue was in fact 3G... things of the past now.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 16, 2010, 06:06:05 am
content: i saw an experiment to test an mcu integrity that are exposed to emp... cant find it anymore in the net. they need a room sized "spooky" machine gun type projected at the chip, and IIRC the mcu preformance is barely distorted. for a backpack size portable emp gen... i dont think it can harm anything, but i dont know. just interpolating from the experiment made.found it! its in my hd... here it is (below). pls note the device they used... well, not a room sized, but i believe thats not portable.

author: Nermash
author_rank: Frequent Contributor
timestamp: November 19, 2010, 09:42:21 pm
content: I would probably handle this as low tech as possible.Since earpieces are magnetic by nature, one short wave of rare earth magnet near the ears of students while entering the exam room, and bang! you have your cheaters before they even entered the room.It is not intrusive, should not be dangerous to those wearing pacemakers, and it doesn't need a lot of time. While student is showing his ID, he/she can be quickly swept. Once you expell first three cheaters, others will become scared, and then you can randomize the testing if you like.KISS rules

author: Psi
author_rank: Super Contributor
timestamp: November 19, 2010, 10:11:06 pm
content: heh, as Nermash said, rare earth magnetThis should dohttp://unitednuclear.com/index.php?main_page=product_info&cPath=70_71&products_id=289It will probably crush someone to death but finding cheaters will be easy as

author: Nermash
author_rank: Frequent Contributor
timestamp: November 20, 2010, 09:17:26 am
content: I was thinking more of a magnet size of the ones you easily find in hard drives, but this one will do alsoIt sure will help decrease hand movement around head and lower examiner energy consumption. You might call it eco friendlyOnly downside is that it can accelerate earpiece from another side of the head, with a lot of force and via the shortest path

author: apex
author_rank: Regular Contributor
timestamp: November 20, 2010, 05:50:24 pm
content: Why don't get such an inductive neck loop earpiece transmitter, modify the sender circuitry and send a message like "Cheating is not allowed in this room. Please contact your system operator.".I'm sure everyone will stop doing it.The idea with the magnet is good, but what if you see parts like scissors or pencils with iron parts moving in your direction.apex

author: k-ww
author_rank: Newbie
timestamp: November 25, 2010, 05:01:04 pm
content: I remember my father  installing a paging system in a retirement home - the transmitter was attached to several loops [2-3] of zip cord [2 conductor] wired as a large loop running around the perimeter of the hallway. Perhaps if you did this in the exam room, around it's perimeter, you could play with a swept signal [audio - low rf [100Khz or so]. This should couple into the earbuds. This is also how a very early house-house system with two coupling coils was set up for 'wireless' comunications between electrical experimentors - they used telephone handsets and batteries to modulate/detect the signals.