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Need tap into Telco line.

Here in rapidly degenerating S.Africa where the judicial system has become non functional, and majority controlling shareholders are looting my inheritance by extracting all value for themselves by way of [self appointed - legally] director's fees, I need some technology leaverage. Obviously in a non-functioning society, you must DIY.

The looter's actions indicate that they are tapping into my phone line which goes through their PABX.

In the telco-room I've located my pair and their pair on the tag-blocks.

How would I best hear their speech ? Since I've got easy regular access to the tag-blocks, and I seldom receive calls, I could set-up occasionally for a few hours at a time. Ie. not use a long-term set-up.

My first thought is to just temporarily connect my pair to theirs, observing the polarity, and while leaving mine on-hook, just tap-off my line into an amplifier, which I can hear while I'm working.

A second refinement, would be to use capacitive coupling to their pair.

I need to terminate my side with a high impedance, so that the capacitive coupling can also have a high impedance. So that it becomes insignificant when I receive or make a call.

If I remove my handset, so that only the audio amplifier terminates my line, during 'listening in', would it work ?

And then by just connecting my handset and/or modem could I expect to operate without significant cross-talk to the looters line ?

Thanks for any info/feedback,

== "James bLond".

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One could use capacitive coupling, but that presents problems: a long line from the tap point to the receiving end will cause severe attenuation. Better would be to amplify the signal at the tap, which then would allow the use of fairly small capacitors; the whole assembly might be hidden nearby and use of thin wires for connection from the block to the assembly would also help hide the work. Alternately, use of a battery powered FET for isolation and "zero" loading of the line might be better; the FET could drive a standard

600ohm:600ohm isolation transformer which *then* could be used to drive your line pair (but not directly, as battery power for ringing and off-hook connection must not be disturbed). Am leaving a bit out..
Reply to
Robert Baer

Had you not put S.Africa - that sounds just like the U.S.

Don't do it, you'll be breaking the law!

Hypothetically speaking:

Assuming all telephones work the same the world over (more or less) a capacitive coupling might be the way to go - the problem is that you may have to use coax to keep the hum down or keep the line short - but at least that is harder to detect. High impedance to a phone line isn't that high - works in your favor a few thousand ohms would be "high."

If they monitor the current - they'd pick up your extra telephone if you wired that into the circuit - but that would have to be done prior to the patch blocks. They'd certainly catch the clicks when you connected, and that would give you up.

Another approach might be to add a tape recorder with a VOX (voice operated switch) and hide that in the patch room. The advantages are no wire directly from you to them and you'd only get caught while checking the recorder. You don't have to be there 24/7 to listen in. The batteries last a long time with a VOX, as does the tape.

Disadvantage is trips to check the tape and replace batteries, risk of getting caught. You might use a wall wart to power the recorder - but check that on your own line first to see that it doesn't introduce hum on the phone lines. You'd still have to change tapes periodically. Any mediocre forensics lab could lift your prints from the equipment.

Add a FM transmitter to the line - if you're reasonably close. Downside is that someone nearby may inadvertently intercept the signal. But it would minimize risk while checking tapes.

Finally - consider an inductive pickup. When I was in high school I bugged my sister's conversations with boyfriends. I had this really cheap cheesy plastic tape recorder with 3" reel to reel tapes. I found the terminal in the basement of the house and added a coil of wire to one side of the line (broke the connection and put the coil

-20 turns of wire ~1" diameter in series with one leg). When she got on the phone I'd slip one of those "pickup" coils that is supposed to go on the earpiece of one's telephone to record the conversation, into the loop I added and recorded the conversation.

You might even be able to slip a pick up coil between the twisted pair for enough signal - never tried it myself so I don't know if it would work. I made a coil and that worked so I had what I wanted and didn't experiment further.

Don't do it!

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Google (how to tap a telephone) got 15 million hits.

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would be my other search.

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Homer J Simpson

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The problem with adding a coil across the line is that it will draw current and very likely "look" like a phone is off hook.

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Robert Baer

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So why make them aware of that? Feed them duff information at strategic points! If I was "them" I would bug your office too and perhaps your car to get more "coverage".

So easy. Not very security conscious are they?

Buy a tape recorder designed for this application (many businesses sell them), find an unused pair, wire that to the buggees pair in the block (preferably on the back side of the blocks so to hide your pair in the mess in there - but, really, would they ever check if anyone can access the terinals?), place the tape recorder at a convenient point on the other end of the pair. That way you only risk being seen messing with the block once.

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Frithiof Andreas Jensen

Not suggesting a coil connected across the line, just adding a coil in series with one leg of the line with a pick up coil to make a transformer. The slight impedance and resistance 20 turns of wire adds in negligible.

Come to think of it one of those audio speaker transformers might also work and might keep the impedance low so no hum is picked up from the line to the listening post.

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Read those documents:

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Connect the output of the circuit to suitable listening amplifier that can send the amplified sound to headphones or some other telephone line.

Cpacitive coupling to the pair and amplification near the coupler is a working approach to listen to signal on telephone line.

Propably not.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/
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Tomi Holger Engdahl

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