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

I read in sci.electronics.design that nina.p20 wrote (in ) about 'Finding a minor Votage drop on a 50V source... It is possible?', on Sun, 6 Nov 2005:

Curious; it came up VERY quickly here. Click - instant page!

I don't think they do. I've seen the specs on 48V input power supplies and IIRC, they can tolerate quite a wide input range. The 48V is (was) used for everything from sensitive computing equipment to powering relays and stuff. Why bother regulating the whole bank's output when a considerable portion of its load isn't very sensitive? Better to put the regulation into only the loads that need it.

Theory: Get money from suckers for marginally useful junk.

Hint: If you find a bug on your line, don't remove it. The snooping parties will just replace it and (maybe) do a better job hiding it the next time. You are better off feeding them some bogus information and otherwise having fun with them.

"nina.p20"

You are incredibly thick.

BTW

Do not post with no visible prior text or the name of poster you are addressing.

Bad etiquette.

........ Phil

I havent seen all the threads in this post, its way too long !.

TDR to find out where the bug is, modify said device with a shotgun, or hire some gentlemen to remove the device

martin

"Anthony Fremont"

@Paul, Thanx for responding,

That's the theory that almost anyone that is bugging business knows. With today's technology, it's a problem to detect or defeat bugs and tapping, but this was NOT my problem, and I really hope I'm not bugged

- and if I am, no one will find my name on SUN or other papers... LOL... The Question was and is ELECTRONICS releated: How the "marginally useful junk" described on many sites work? How they can measure a line voltage drop from a high impedance Parallel tap or a series one? How is a simple tap defeated by "marginally useful junk" ? If you think you may have any answers, I'll be very glad to get :) Regards, Nina

Hi Ken,

Ken, nothing to do rf this or about paranoia... I know the theory and I'm not looking for taps or afraid to be tapped :) As I've answered to Paul earlier, The Question was and is ELECTRONICS releated: How the "marginally useful junk" described on many sites work? How they can measure a line voltage drop from a high impedance Parallel tap or a series one? How is

a simple tap defeated by "marginally useful junk" ? If you think you may have any answers - or any schematics, I'll be very glad to get :) Cheers, Nina

With respect, you're trying to detect the connection of a >10MOhm load onto a phone line, so you're test/monitoring circuit will need an input impedance way higher than that. *If* the phone line is always the one you've measured, then maybe it will always deliver 48.003V as measured. However the voltage delivered is only *nominally* 48V - the fact that your particular line delivers 48.003 is a nice coincidence. You have a good condition pair and/or are close to the exchange. It doesn't take much crap in a joint (or change in load at the end of a line) to change the conditions you are seeing. This is not to say that it can't be done, just that it is not easy (see other posts referring to ppm - voltage dividing the input down will not reduce that requirement).

I only looked at the first of the devices you gave links to but I would suspect it would not detect a 10MOhm load being placed on the line. They mention detecting when another extension is lifted, so I would strongly suspect that they are looking for much coarser load changes, probably (surprise surprise!) a nominal telephone load. There's acronyms for all these things, but I'm jet-lagged and the letters won't come to me. :-)

Incidentally, a 'tap' is just not done on the physical line these days. It's done via the software in the exchange. No-one with any credibility would do a physical tap (hack! spit!) in this digital age.

Cheers.

Ken

"Anthony Fremont"

Even the model number of the Fluke DMM as wrong.

Stick you head up your fat arse - you posturing prick.

" 10mV divided by 5 uA = 2000 ohms. Seems about the right source R for a phone line. "

That aint no specification - you posturing ass.

I have raised the appropriate doubts and shown the numbers make no sense.

The OP now has to think it all through.

....... Phil

"John Woodgate"

The OP has to get over the idea that line voltage is precisely fixed and that detection of a 5 uA load that has been there for a time is possible by voltage measurement.

That is steady progress.

......... Phil

@Phil,

I cannot be sure of those that appears on the links I've sent, but seen several devices on a "spy-store" in UK and on a security exhibition on my country that seems to make the same jobs. From what I've seen so far they DO their jobs. I don't know about the particular devices on the links I've sent, but for 165$ or more - I assume they do.

How do you know that they really do NOT?

Cose no "pro" in Electronics, *including you*, may give another practical idea... just empty words or flames....

IMHO, that's what an INSANE do. If a person that suspects it is tapped and wants to take any measures, or a paranoid, purchase a device like that, and spends his\\her money instead going to a proffesional bureau, OK , I can understand. Just for curiosity - nope... IMHO again...

All I'm interested is the principle of detecting and defeating taps, the simple and popular ones - the electronic part. I'd like to see any schematic, but no one - up this moment - was able to show his\\her electronic skills....

All I see is philosophical blah blah, and a lot of cheap cynical blah from some of the ppl who answer....

Cheers, Nina

"nina.p20"

Forget Google Groups - it cannot access Binary Newsgroups.

Get yourself an ISP that provides a " news server " with direct access to usenet !!

Find " alt.binaries.schematics.electronic "

........ Phil

@Ken,

Yes Ken that what I was looking for from the beginning !!! A voltage drop on the line !!! Nothing complicate or sophisticate.... :) I *assume* that is the way the things are done... My second problem was how they are supposed to be feed from the line, as they are loading the line themselfs, and the only thing I've "suspect" is that they are connected somehow in series with the line, detecting the *nominal* voltage and voltage drop. How is it done, I don't really know, and I'll be very glad to get any practical help. The question "HOW TO DEFEATE" the *simple* bugs on line, all I've got is by a shoot-gun, or my own suggestion - a 500V Megger... There is a posibility that the members of this discussion simple does not know the answers, and hiding that with "wise" answers instead of just keeping "low profile"... Or just bad will to help... I really don't know, as I'm really new at NG... You are one of the *few* persons that responded to my question with a serious professional answer and *tried* to help, even I'm still looking for a more practical help :)

Cheers, Nina

"John Woodgate" Phil Allison

" Excellent - JW has caught up to what I posted 30 hours ago. "

" Maybe the OP really meant the Fluke 179, 6000 count, hand held meter.

On its 60 volt DC range the resolution is 10 mV.

Not 10 uV.

10mV divided by 5 uA = 2000 ohms.

Seems about the right source R for a phone line. "

" Maybe my explanation is easier to understand."

......... Phil

"Damir"

Quote:

" If the 48 volt has a source R of 1000 ohms - what voltage drop does 10 Mohms cause ? "

Damir:

" 5mA "'

Wow.

......... Phil

Hey Phil, Go check your blood pressure...

You assume that or are you sure?

I see you have some self - experience with Demente... as well with nonsense....

Well, I hope you are not offering me that from your own experience, and if it IS from YOUR experience, please let us know any "succulent" detail... :)

Go check th blood pressure again, I'll be very sad if the world may lose someone like you... :(

Nina

"John Woodgate" "nina.p20"

How about you quote the post where I addressed the OP in "real bad language" .

I will not hold my breath waiting.

.......... Phil

"Fred Bloggs"

.......... Phil