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Guide To Wire Tapping

Here is some info on phone taps. I have enclosed a schematic for a simple wiretap & instructions for hooking up a tape recorder control relay to the phone line.

First i’ll discuss taps a little. There are many different types of taps. There are tranmitters, wired taps and induction taps to name a few. Wired and wireless transmitters must be physically connected to the line before they’ll do any good. Once a wireless tap is connected to the line, it can transmit all conversations over a limited range. The phones in the house can even be modified to pick up conversations in the room & transmit them too! These taps are usually powered off the phone line, but can have an external power source.

Wired taps, on the other hand, need no power source, but a wire must be run from the line to the listener or to a transmitter. There are obvious advantages of wireless taps over wired ones. There is one type of wireless tap that looks like a normal telephone mike. All you have to do is replace the original mike with this & it’ll transmit all conversations!

There is an exotic type of wired tap known as the ‘infinity transmitter’ or ‘harmonica bug’. In order to hook up one of these, you need access to the target telephone. It has a tone decoder & switch inside. When it is installed, someone calls the tapped phone & *before* it rings, blows a whistle over the line. The x-mitter receives the tone & picks up the phone via a relay. The mike on the phone is activated so the caller can hear all conversations in the room.

There is a sweep tone test at 415/bug-1111 which can be used to detect on of these taps. If one og these is on your line & the test # sends the correct tone, you’ll hear a click.

Induction taps have one big advantage over taps that must be physically wired to the phone. They don’t have to be touching the phone in order to pick up the conversation. They work on the same principle as the little suction-cup tape recorder mikes you can get at radio shack. Induction mikes can be hooked up to a transmitter or be wired. Here is an example of industrial espionage using the phone: a salesman walks into an office & makes a fone call. He fakes the conversation, but when he hangs up he slips some foam-rubber cubes under the handset, so the fone is still off the hook. The called party can still hear all conversations in the room. When someone picks up the fone, the cubes fall away unnoticed. I use a tap on my line to monitor what ae-pro is doing when it auto-dials, since it doesn’t take advantage of the handset on the apple cat ii. I can also hook up the tap to a cassette recorder or amplifier.

Here is the schematic:


The 100k pot is used for volume. It should be on its highest (least resistance) setting if you hook a speaker across the output, but it should be set on its highest resistance for a tape recorder or amplifier. You may find it necessary to add another 10-40k. The capacitor should be around .47 mfd. It’s only purpose is to prevent the relay in the co from tripping & thinking you have the fone off the hook. The audio output transformer available at radio shack (273-1380) is fine for the x-former. The black & green are fine for input & the red & white go to the output device. You may want to experiment with the x-former for the best output. Hooking up a tape recorder control relay is east. Just one of the fone wires (usu. Red) before the telephones & hook one end to one wire of the relay & the other end to the other relay wire. Like this:


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