This advanced unit tests every possible combination of wires in a four wire cable. This lets you detect some of the more sophisticated taps that use split pairs.Advanced Wiretap Detector TT-46While not much can be done about down-line taps, the TT-46 will help you check your phone lines for on-premises series and parallel bugs and wiretaps. You can also check your telephone for the most common types of hookswitch bypasses. (A hookswitch bypass is a modification to the telephone instrument that causes the transmitter or receiver in the telephone handset to pick up room sounds and pass them down the phone line even with the phone hung up. This effectively turns the telephone into a room monitor.) The TT-46 detects series devices with a resistance of 10 ohms or more. (Most series taps have a resistance of over 100 ohms.) It also detects parallel devices with a resistance of 65 megohms or less. (Most parallel taps are under 30 megohms.) It can also detect certain capacitively coupled taps. Advanced Wiretap Detector TT-46Also included in the TT-46 is a line monitor that lets you check the wire pairs for the presence of room audio when the phones are hung up. (The presence of room audio on the phone line when the telephones are not being used is a sure sign of bugging.) A line driver is part of the monitor function. The line driver is used to turn on (activate) any voltage operated microphones, such as FET mics, that may be connected to a pair of wires. The unit weighs 9 oz. and measures 7" x 4.6" x 2.25" (with the cover closed). It is powered by one 9 volt alkaline battery (included). Also included are all necessary cords, plugs and adapters along with an illustrated instruction manual.