Finding a minor Votage drop on a 50V source... It is possible?

Hmm.... (5mA)*(10Meg) = (5*10^-3 A)*(1*10^7 ohm) = 5*10^4 volts. Someone is slightly off...

That is why those units are so over-priced, to convince the prospective buyer that they do work, make them less likely to become suspect, and less willing to admit a bad decision after the purchase. The professional firms who specialize in detecting and locating taps do not use them at all and refer to them as "toys." The only reliable method is physical inspection of the wiring followed with an array of RF direction finding and line monitoring for remote control signaling techniques. I suggest that most of the demonstrations you witnessed were rigged and fraudulent, and that at best these products may be used to detect a very amateurish tap job.

This link is too funny, but it gives some useful information on the inductive tap which usually cannot be detected. There is a higher variant called a split/resplit that even the TDR cannot detect.

Not really because the "defeaters" are all junk electronics in the same grade as magic magnetic cure-all stimulators and that kind of thing. The only sure way is a cooperative call to similarly equipped receiver- convert the audio to digital, encrypt , and send- like a modem. Then the interceptors are useless.

"John Woodgate"

How pathetic.

........ Phil

"Anthony Fremont"

More your comfort zone.

......... Phil

I hear that also works when you need to dig up the back yard to plant potatoes. ;-)

Cheers! Rich

"nina.p20"

You are making wild assumptions - IMO.

You are making wild assumptions - IMO.

That is what any sane person would do.

......... Phil

your particular line

and/or

It's

do

No problem about the legal vs non-legal taps - I wasn't sure what level of paranoia (LOP) or otherwise we were dealing with. :-)

If you're dealing with a tap that sends off the received audio via an RF link (which is implied in what you say) then a (radio) scanner can be used to sweep across the spectrum (assuming you don't have your trusty spectrum analyser sitting idle in the toolbox). Again assuming an idiot has tapped your line, they'll use an easy frequency such as FM radio, baby-monitors, cordless phones, 220MHz and 413MHz bands and the like use. Maybe CB or ham frequencies but I'd be betting the others. That just narrows the list down for 'ease' of detection, but whether this is a convenient thing to do before every phone call depends on LOP as mentioned previously. Once you know the TX frequency you can deal with it as felt appropriate (or as Paul has mentioned elsewhere, leave well enough alone).

Cheers.

Ken

IIRC, at least one of the ads claimed the ability to detect "low to medium impedance taps". Without specs (which I didn't see and I doubt they make easily available), they have an 'out' in that any tap they can't detect must be one of those high impedance ones, which the ad disclaimed and so you don't get your money back. For all I know, these things might no be able to detect anything less than a second phone on the line.

I don't think this thing 'defeats' the taps outright. I depends on you to observe the tap indication and not use the line if its bugged. Not very high tech if you ask me.

"nina.p20"

Is you real name "nincompoop" ?

............ Phil

of

used

spectrum

ham

down

before

the

Hiya.

Yup, we're movin' along away from the original question(s), true to 'net fashion. :-)

Apart from a very high impedance comparator looking for a difference from either a known voltage (if you knew the original voltage anyway) or the nominal voltage (and then you assume that any change from that is due to a bug and not a line condition); or if your circuit can also detect the RF that may be emitted by a bug (and then it'll only work if the bug is in the immediate vicinity) then I can't see how you can do it reliably. And as you've also pointed out, an inductively coupled bug won't be detected by a voltage sensing method, nor will a hi-Z device.

This isn't to say it can't be done, but it wouldn't be $100 at your local snooping shop (wish I still had a German catalog I got hold of some years ago - many bits of kit for just this sort of work, but nothing was cheap!). Too many variables for my liking.

Cheers.

Ken

...

If you think your phone is tapped, then when it rings, answer, "F*ck the Homeland Security nazis!"

And, to make your drug deals, of course, you walk down to the pay phone at the corner. ;-}

Good Luck! Rich

I would "whack" the line with a decent pulse, up to maybe 200 volts, for a few microseconds and see what comes back in the form of reflections on an oscilloscope.

The reflections should match the physical layout of the line, there should be one where the line is terminated in the junction box f.ex. - a listening device might show up because one triggers the over-voltage protection on it.

If the tap is magnetic, it might not show up. If it is government, it is via the "lawful interception interface" built into the exchange and you are screwed anyway.

Look up "time domain reflectometry" in Google.

I read in sci.electronics.design that Frithiof Andreas Jensen wrote (in ) about 'Finding a minor Votage drop on a 50V source... It is possible?', on Tue, 8 Nov 2005:

Especially if he sweeps the girl and not the room. (;-)

The same way politics, organised religion or herbal medicine "work": It provides a framework for the transfer of money from the purchasers account to the sellers account. Fulfillment of expectations, that's what it is about.

If the commercial product does not detect any bugs, does it really matter to anyone? Think about it.

Where do you *live* anyway - you seem lacking in your understanding of marketing??

HINT:

The paranoid will buy one product after another until he finds one that does indeed "detect" the bugs he "knows" are there; the sceptic will tests the product, find that it does not work, return it for a refund and that's that.

The random luser will be depressed over that he is not important enough for anyone to be bugged and in due time he will also discover that it does not impress girls to do a bug-sweep in front of them.

The criminal/spy will be up against Government - the only reason he may find bugs is because "they" need to divert attention from the real sources of information!

Because You are just yet another Trolling Cunt.

The answers have been given to you.

Yet you continue like a broken record - or News2020 - except you lack newsies stile and inventiveness.

Nobody *cares* about your opinion.

Which have been provided in sufficient detail for anyone with a basic grasp of electronics

Nobody has to qualify themselves to you

Yep, that is indeed *all* you can see - a reflection of your own worth, I guess.

The pay phone is *absolutely* bugged: there are so few of them that 100% automatic surveillance is possible.

For "security", stolen mobiles is about the best you can get - closely followed by VOIP + IPsec. If someone is watching they will of course notice that the traffic is encrypted and start to deploy countermeasures.

Security from government is about not attracting attention in the first place, doing the same as everybody else; so an "Echellon Google" on your profile will give about 20 Million "Hits" to read through manually.

Like when Baader-Meinhoff decided to pay their utility bills with "untraceable" cash - which about 15 people in Hamburg did at the time ;-).

Google Groups Newbie Primer: