Normally people entering rooms have to pass through doorways. I would think any "open mike" that responds to the pattern should be considered a threat.
But look, you can believe what you want, your world can be a much simpler place, if you don't delve into these issues.
Luck; Ken
The signals are fairly constant, encoded bits regardless of whether there's silence or not. My argument is not whether the mere presences of signals can be deteced, but rather there is a significant enough difference in signal to detect with sound input versus silence (in the room).
Claiming you will see different currents based on the data is easy with the gear open and measurement by wire. Trying to find whether there is an unknown device present or not is not quite same situation.
Sure, but we haven't established that it really will be detectable based on a pattern of sound. Presuming it will because some other type of device can be detected isn't reliable.
This is a fairly generic non-applicable comment. We could as easily consider the opposite, that you can believe what you want and your world can be a much more paranoid place if you don't delve into the specifics- but either way we cannot assume detection without any evidence of same type device BEING detected in an applicable scenario. While a doorway detector could be more easily implemented than some, it's also not going to detect a device turned off at the time.
We'll have to consider the specifics of a digital recorder, and perhaps even more significantly one that might be chosen to be harder to detect if it were to be used for a stealthy purpose.
maybe you should step out of the dark and into the real world. have you ever use a service monitor to scan a wide spectrum of frequencies? i can tell you that wide band receivers on a mini board exist and are very sensitive to external R.F. when your standing beside the person with in 3 feet of them. most devices these day's involve embedded processes which also uses R.F. clock devices. it would take a very high priced unit with proper casing and shielding to reduce the emissions low enough for this device to not detect it. most consumer electronics is very sloppy in the area. in fact, there has been cases where cheaply made devices that xfer lets say audio information in a digital format causes their internal osc's to be unstable enough when voice is passing through the mic/pre'amp circuits, that some one with a high gain FM receiver can detect clear enough audio from a distance before it even gets encoded digitally for final destination. the average joe wouldn't even think of this let alone attempt to waste their time in trying it how ever, there are people out there that spend a lot of time investigating consumer devices just for the purpose of simple wireless taps and detection of use.
-- Real Programmers Do things like this. http://webpages.charter.net/jamie_5
I have used a spectrum analyser. I admit I am not an EMI expert. However cellphone detection is far simpler than detection of other devices....
Oh, I know. But I was pointing out that the guy described does not need to have what he claimed. And in addition, how do you separate, e.g., the crystal in a high-powerd pocket calculator from the one in the MP3 recorder? Detecting RF energy is not that difficult. It becomes difficult if you have a lot of background noise or need an identification in addition.
Arno
You man there actually is something which will detect MP3 recorders?
No problems.
This is to document something quite serious.
There are devices that can detect when electronic devices are being used. There are devices that can be made that can detect almost any known material If said mp3 player is made of that material it can be detected.
Which is not entirely applicable, since plenty of non-recorders are made of circuit boards, ICs & other discretes, and some plastic. Cell phone and pager are two quite common ones.
Detecting electronics devices in general, is it useful? We dont know the exact scenario, what the result would be of a positive detection but as above, cell phones and pagers would tend to be caught and are going to be far more common and innocuous than a recording device, though in the former case, the phone may have recording capability too.
material
Sure it is
Yep, and all are detectable, and all have signatures.
Depends on who you ask The OP is not the only one who wants to ensure no one is able to record conversations, or hear conversations they should not be hearing.
He gave the scenario.
True enough, but the technology is there to do what is being requested. Now if the OP can afford it, or even obtain it is a different issue.
You'd be surprised where people can hide things:
Caution! NSFW!
max
material
And what is a common item to circuit boards, IC's, cell phones, pagers, MP3 players, etc. There are devices made to detect the presence of semiconductors, and these have been out for ages. And now with the war on terror going on, you would not believe what kind of sensors they are coming up with. Minor modifications of some of these units would not be very difficult to detect a mere MP3 in someones pocket. But then these would not be cheap either, if you can even get one.
Well shielded (for example, wrapped to copper foil), 1.5V AAA powered device will give EMI below ambient level. If its clock generator employs spread spectrum, it's even more difficult to detect.
Are you the trying to be the documenter, or trying to avoid being the documentee? Or both?
Detection is a minor problem. Correct identification is the issue. This is likely infeasible, unless you have the specific recorder in question beforehand. And remember that you wanted to know whether it is recording. Even more difficult....
Arno
max wrote in news: snipped-for-privacy@4ax.com:
Sure, but I don't think the MP3 recorder would work very well in there, so the point is moot.
-- ybbxvatyvxrnobeantnvayvivatyvxrnurergvpyvfgravatgbneguheyrrerpbeqfznxv atnyylbhesevraqfsrryfbthvyglnobhggurveplavpvfznaqgurerfgbsgurvetrareng vbaabgriragurtbireazragnertbaanfgbclbhabjohgnerlbhernqlgborurnegoebxra
Nope, not without the scenario.
You have not established that the signature (difference) of such a device can be discriminated from a different device. The scenario has not been defined enough to know if the device will be turned on within the distance of the scanner/other detection device.
Random ideas that "something" similar is possible is not same as application in a specific scenario.
No. A hint, but not a full scenario might include something like what happens if "something" is detected, both the full purpose and result.
You have not established this. That some fields can be detected, that it can be known if something is running, is not same thing as knowing a digital recorder is running. This difference is quite important in many scenarios because OTHER types of devices are far more common in modern society than digital recorders.
Yes, which is one of the reasons why detection of these won't help, unless ALL such devices are banned which is unlikely... but again, we dont have the specific scenario to consider.
I would believe you are taking a random unfounded presumption that someone "could" be possible without supporting evidence, nor consideration of what would be necessary to distinguish this particular device.
Unfounded speculation. "Maybe" it's easy enough to detect the device when turned off. "Probably" if you were close enough to the device you could even detect that it's turned on. That's a far cry from identification as an MP3 player, let alone one that is recording, vs another mode of operation (like playback, wouldn't it be highly possible someone who has an MP3 player, would have it to play MP3?)
Establish that such a device exists at all, that can detect an MP3 player recording, specifically discriminate it from other devices. Nevermind if we can buy it or how much it costs, establish that it can be done at all as so far you have not.
used.
Sure it is.
It is being done today.
To detect semiconducter junctions the operating state of the device being measured is not important.
The scenario was presented with enough detail.
Now
Your lack of knowledge of the systems involved is not my problem. The technology does exist to do what the person wants. Now how large this equipment is, and how much it costs, and even if it is available to us regular joe blows is something different.
>
used.
MP3
Depends on the OP, his office can ban those items in the work place. The point remains they are detectable.
these
of
Nope.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.