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The inductive method is the safest and most widely used.
Telephone radio transmitters connected directly to the telephone line have proven themselves in practice, but they have a very big drawback - they are easy to detect and "suppress". Recently, contactless removers have become widespread. They are almost impossible to suppress by any electronic means, since they operate on the principle of inductive coupling with the telephone wire. In addition, contactless removers are easy to install and do not require skills in working with electronic equipment.
Let's consider the device of a contactless sensor shown in the figure below.
Two ferrite cups 1 and 4 are used as the sensor body, which are also a magnetic circuit, into which a polystyrene frame is inserted (not shown in the figure). A coil containing 600 turns of PEV-1 0.05 mm wire is wound on the frame. A shielded wire 5 is soldered to the ends of the coil, which is brought out through the slot in the upper cup 1. A connector for the microphone input of the voice recorder is soldered to the other end of the wire, to which the a signal is sent from the sensor.
The cups are fastened together with a screw 2 with a spring 3 put on it. When connecting the sensor to the telephone line, cups 1 and 4 are moved apart, and a telephone wire 6 (only one - any of the two) is inserted into the magnetic circuit. As a result of mutual induction, the signal from the telephone line is induced on the coil, which acts as a secondary winding of the step-up transformer.
It should be noted that the sensor works well only with dictaphones from SONY, OLIMPIK, SANYO. In order for the sensor to work well with other dictaphones, as well as to increase its sensitivity, it is advisable to assemble an amplifier for it.
The inductive method is used for fiber optic communication lines (FOCL), both contact and contactless.
1. For contact connection, remove the protective layers of the cable, etch into the reflective sheath and bend the cable to the required angle. In this case, it is very difficult to detect a connection due to leakage (signal power weakening), since it is enough to select 0.001% of the transmitted power to eavesdrop on the conversations.
2. The basic diagram of a contactless connection to a fiber-optic communication line is usually implemented either during the installation of the fiber-optic communication line or during dismantling and repair of the equipment, since a glass tube rigidly fixed on a pre-stripped cable, sealed on both sides and having a curved branch, at the end of which a lens is installed, focusing the light flux on the LED, an electrical signal from which is fed to the amplifier and the final receiving device.
Telephone radio transmitters connected directly to the telephone line have proven themselves in practice, but they have a very big drawback - they are easy to detect and "suppress". Recently, contactless removers have become widespread. They are almost impossible to suppress by any electronic means, since they operate on the principle of inductive coupling with the telephone wire. In addition, contactless removers are easy to install and do not require skills in working with electronic equipment.
Let's consider the device of a contactless sensor shown in the figure below.
Two ferrite cups 1 and 4 are used as the sensor body, which are also a magnetic circuit, into which a polystyrene frame is inserted (not shown in the figure). A coil containing 600 turns of PEV-1 0.05 mm wire is wound on the frame. A shielded wire 5 is soldered to the ends of the coil, which is brought out through the slot in the upper cup 1. A connector for the microphone input of the voice recorder is soldered to the other end of the wire, to which the a signal is sent from the sensor.
The cups are fastened together with a screw 2 with a spring 3 put on it. When connecting the sensor to the telephone line, cups 1 and 4 are moved apart, and a telephone wire 6 (only one - any of the two) is inserted into the magnetic circuit. As a result of mutual induction, the signal from the telephone line is induced on the coil, which acts as a secondary winding of the step-up transformer.
It should be noted that the sensor works well only with dictaphones from SONY, OLIMPIK, SANYO. In order for the sensor to work well with other dictaphones, as well as to increase its sensitivity, it is advisable to assemble an amplifier for it.
The inductive method is used for fiber optic communication lines (FOCL), both contact and contactless.
1. For contact connection, remove the protective layers of the cable, etch into the reflective sheath and bend the cable to the required angle. In this case, it is very difficult to detect a connection due to leakage (signal power weakening), since it is enough to select 0.001% of the transmitted power to eavesdrop on the conversations.
2. The basic diagram of a contactless connection to a fiber-optic communication line is usually implemented either during the installation of the fiber-optic communication line or during dismantling and repair of the equipment, since a glass tube rigidly fixed on a pre-stripped cable, sealed on both sides and having a curved branch, at the end of which a lens is installed, focusing the light flux on the LED, an electrical signal from which is fed to the amplifier and the final receiving device.
