The Invisible Box   Version imprimable de cet article

The invisible box will make it so that when you pick up a phone on your phone line any of those in-use lights that tell if an extension phone is picked up, wont light and automatic recording devices that record when any extension in the house picks up will NOT record when an invisible box is in use

par g0uZ

- Introduction :

My friend’s dad used to record all of his conversations by putting an automatic recording device on an extension in a locked room, short of disconnecting the extension from the TNI, the invisible box is the PERFECT soloution.

- Theory :

The theory is based off the same principles as the infamous blackbox that used a 1.8k
resistor to keep the phone line at 50v when you pick up, which actually still works, but
because of SS7 the voice path is cut off from the party calling you, and the phone company
doesn’t allow a voice connection any more until your phone goes off hook and there’s
supervision. The invisible box works by using high resistance to keep the voltage at
about 20 volts. This is accomplished by placing a resistor of about 470ohms in
series with your phone. The phone is approximately 215ohms and draws 28ma of current, which
means when your phone is off-hook there is approximately 6 volts on the phone line. When
you place the resistor in series with the phone line there is a total resistance of 685ohms.
Using ohm’s law, 685 ohms times 28ma gets you 19.2 Volts ! So the resistor keeps the phone
line at about 20 volts, and most in use lights only go off when there is about 15 volts or
less on the phone line.

- Construction :

You will need a phone cord and a 470ohm resistor(Yellow, Purple, Brown). You can get the
resistor in a 5 pack at radioshack for $0.49. It wouldn’t hurt to have some wire stripers,
and possibly electrical tape or solder. Strip the phone cord in the middle, dont cut the
modular jacks off. You’ll see 4 or 2 wires, usually black, red, green, and yellow. Dont
worry about the black and yellow wires, in fact cut them off they’ll get in the way. Leave
the green wire alone, thats the positive wire, and sense current flows from negative to
positive and we’re trying to opose current so the voltage wont drop we leave it alone !
Finally, cut the red wire (that’s the negative !) in half and strip both ends, you’re going
to insert the resistor here.

- Diagram :

(-) Red wire  470ohm
(+) Green wire

- Conclusion :

That’s it, pretty simple huh ? You might be thinking that maybe there is no real use for
this because all it does it make it so that an in-use light doesn’t light when you pick up
the phone. But think of the possibilities, you could go beigeboxing with this box and it
might save you if the person your beigeing off of has an in-use light and they always look
at it to see if their kid is on the phone, but because of your trusty invisible box hooked
up to the phone line that light never comes on and they never pick up to yell at what they
would think is their kid. Personally, I use it when I’m talking on my phone line but want
to use my main line to go on the internet, my mom is always checking that damn in-use light
and yelling at me, "You’re on the internet with my phone line ! GET OFF NOW !" HA-HA ! Now
she’ll never know ! The sad thing is I bet this even bypasses those lame $200 phone tap
detectors you always see on TV.

Okay time for greets :

Yari my beloved !, Spoonm !, Pooly, BigB9000, Xhype, Gizmo, Morbid Angel, Lancomandr,
phlux, cry0, syncron, Omega2, ! and anyone else I left out !


After recently purchasing the 43-443 in-use light from radioshack, I noticed
that they detected current, not voltage, unlike the in-use light on my mom’s phone that only
detects voltage drop. However you can defeat these by placing a 220ohm resistor in parallel
with the phone line and when your using your phone there won’t be enough current to light
the light. I have made an improved "invisible box" that defeats both the voltage and current
detector in-use lights. Below is the diagram :

Ring(-)   470ohm
                    < 220ohm

If your in-use light still lights trying changing the resistor values as the resistance
of your phone may vary.

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