The Invisible Box
by Lucky225
Introduction: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 alert if an extension phone is picked up - won't light.
Theory
The theory is based off the same principles as the infamous Black Box that used a 1.8 kω resistor to keep the phone line at 50V when you pick up. It actually still works, but because of modern switching, the voice path is cut-off from the party calling you, and the phone company doesn't allow a voice connection anymore 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 470 ohms in series with your phone. The phone is approximately 215 ohms and draws 28 mA 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 685 ohms. Using Ohm's law, 685 ohms times 28 mA 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 470 ohm resistor (yellow, purple, brown). You can get the resistor in five-pack at Radio Shack for $0.49. It wouldn't hurt to have some wire strippers and possibly electrical tape or solder. Strip the phone cord in the middle. Don't cut the modular jacks off. You'll see four or two wires, usually black, red, green, and yellow. Don't worry about the black and yellow wires. In fact, cut them off they'll get in the way. Leave the green wire alone. That's the positive wire, and sense current flows from negative to positive and we're trying to oppose current so the voltage won't 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
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 Beige Boxing 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. 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.
Yari my beloved!, Spoonm!, Pooly, BigB9000, Xhype, Gizmo, Morbid Angel, Lancomandr, phlux, cry0, syncron, Omega2, and anyone else I left out!
Update
After recently purchasing the #43-443 in-use light from Radio Shack, 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 220 ohm 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:
Red Ring(-) 470ohm ---------/\/\/\-------> < 220ohm > ----------------------- Tip(+) GreenIf your in-use light still lights, trying changing the resistor values as the resistance of your phone may vary.