Here is some info on phone taps. In this file is a schematic for a simple wiretap & instructions for hooking up a small tape recorder control relay to the phone line.
First, I will discuss taps a little. There are many different types of taps. There are transmitters, wired taps, and induction taps to name a few. Wired and wireless transmitters must be physically connected to the line before they will do any good. Once a wireless tap is connected to the line, it can transmit all conversations over a limited reception range. The phones in the house can even be modifies to pick up conversations in the room and transmit them too! These taps are usually powered off of the phone line, but can have an external power source. You can get more information on these taps by getting an issue of Popular Communications and reading through the ads. 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 and it will transmit all conversations! There is also an exotic type of wired tap known as the 'Infinity Transmitter' or 'Harmonica Bug'. In order to hook one of these, it must be installed inside the phone. When someone calls the tapped phone & *before* it rings and blows a whistle over the line, the transmitter picks up the phone via a relay. The mike on the phone is activated so that the caller can hear all of the conversations in the room. There is a sweep tone test at 415/BUG-1111 which can be used to detect one of these taps. If one of these is on your line & the test # sends the correct tone, you will hear a click. Induction taps have one big advantage over taps that must be physically wired to the phone. They do not 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 that 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 phone call. He fakes the conversation, but when he hangs up he slips some foam rubber cubes into the cradle. The called party can still hear all conversations in the room. When someone picks up the phone, the cubes fall away unnoticed.
A tap can also be used on a phone to overhear what your modem is doing when you are war-dialing, hacking, or just pl ain calling a bbs.
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 phone from tripping & thinking that you have the phone off of the hook. the audio output transformer is available at Radio Shack. (part # 273-138E for input). The red & the white wires go to the output device. You may want to experiment with the transformer for the best output. Hooking up a tape recorder relay is easy. Just hook one of the phone wires (usually red) to the end of one of the relay & the other end just loop around. This bypasses it. It should look like this:
(part #275-004 from Radio Shack works fine)
If you think that you line is tapped, the first thing to do is to physically inspect the line yourself ESPECIALLY the phones. You can get mike replacements with bug detectors built in. However, I would not trust them too much. It is too easy to get a wrong reading.
For more info:
BUGS AND ELECTRONIC SURVEILLANCE from Desert Publications HOW TO AVOID ELECTRONIC EAVESDROPPING & PRIVACY INVASION. I do not remember who this one is from... you might want to try Paladin Press.