Help on wire line monitoring tools.

Help on wire line monitoring tools.

Help
on wire line monitoring tools,
evaluation of LVO-50 line analyzer parameters

Wire line monitoring tools designed to detect unauthorized connections to them in order to organize information leakage channels can be conditionally divided into three classes:

1 — line signal monitoring tools— LF signal amplifiers, broadband HF signal indicators, tunable receivers of modulated HF signals; this class may include autodyne receivers;
2 — means of monitoring normalized parameters of lines (both active and disconnected from consumers and sources; both direct and alternating current) — monitoring impedance, voltage, current;
3 — means of monitoring line parameters based on the principle of active influence on the line and detection of anomalies caused by the reaction to it of devices connected to the line.

Means of monitoring wire lines can be implemented as “watchdog” or “search” ones.
Both of them can combine the functions of devices of different classes of the proposed classification.

The following devices can be given as class 1 devices: ST 031 “Piranha” (Russia), “Oblako” (Russia), SRM-700 (foreign).

The devices of the 2nd class may include Winkelman Model 200/B (foreign), KTL-2 (Russia), KTL-400 (Russia).

The devices that combine the functions of the 1st and 2nd classes include TSM-03 (foreign), TPU-5 (Russia), “Bager-01” (Russia), etc.

The devices of the first class detect signals from devices that are unauthorizedly connected to the lines and allow:

• listen to the low-frequency signal in the line, identifying its connection with the acoustic signal in the room (the presence of connected microphones, devices with a microphone effect, etc.);
• identify the presence of the so-called high-frequency probing signal or a constantly operating signal transmitter in the line with a level exceeding the level of its own signals in the line or the natural background of high-frequency interference at the point of connection of the monitoring device;
• identify the presence of a high-frequency signal, the modulation of which is associated with the acoustic signal in the room;
• detect the presence of modulation of the probing high-frequency signal, which is associated with the acoustic signal in the room.

The second class of means detects differences in the normalized parameters of lines with and without connections to them. The bulk of control means, conditionally, of the second class — these are passive meters of resistance, capacity, voltage, current, adapted to measurements in wire lines with the necessary switching, automation, interpretation of readings, etc. introduced into the measurement circuit.

The detection ability of such means, especially those that control active and non-disconnectable lines during the control process, does not exceed the natural spread of the parameters of real lines. Detection of connections to lines consists of detecting the difference in measured parameters from the average statistical values ​​of «clean» lines or from previously measured values ​​for specific lines.

The use of first and second class agents can give a noticeable effect with constant (in “watchdog” mode) or periodic monitoring of specific lines.

Manufacturers of wire line monitoring devices, as a rule, provide their parameters expressed in generally accepted radio engineering quantities and do not provide the parameters of devices that can be detected with their help, limiting themselves to statements such as: “ensures detection of any “devices from the installation site to the automatic telephone exchange”; “false alarms are excluded…” etc. In some cases, such devices do not allow detection of devices connected to telephone lines with an autonomous power supply, including a household tape recorder, as well as a parallel telephone with the receiver hung up, etc.

The third class of wire line monitoring devices in the proposed classification may include reflectometers and so-called non-linear wire line locators.

Reflector meters— devices designed to detect irregularities in the wave impedance of the analyzed line. These include industry-produced standard line irregularity meters such as R5-10, R5-11 (Russia) and devices designed to monitor wired communications during their comprehensive testing for information leakage, such as “Bor-1” (Russia) and 1205T (foreign).

Reflectometers are based on feeding a pulse signal into a line and receiving a signal reflected from a line irregularity. By the delay of the reflected signal, knowing the line parameters, it is possible to determine the distance to the irregularity (a «defect» in the line). The capabilities of reflectometers, like any equipment, are limited by their sensitivity. The defects of the «open circuit» and «short circuit» types are detected best, while, for example, connections to lines with a resistive input impedance of several tens of kOhm are not detected by them in principle. In addition, it is very difficult to control branched wire communications, for example, power lines, since it requires monitoring each branch separately.

Considering the differences in the wave resistance of different types of lines, in practice each specific line requires calibration of the device. The use of reflectometers is effective if you “store an image” of a known “clean” specific line and use it to periodically monitor it.

Nonlinear locators of wire lines— devices based on the detection of harmonic components of the test signal in the line, caused by connecting devices with nonlinear input impedance to it.

Network power supplies of the pickup devices have a significant level of nonlinearity of the input impedance, since they perform a nonlinear conversion of alternating current into direct current. In this case, the level of nonlinearity of the input impedance is proportional to the power in the load of the power supply. This allows expressing the detection characteristics of nonlinear locators of wire lines through the power of the detected network power supply. Receivers and transmitters of information also have nonlinearity of the input impedance, since they contain semiconductor elements.

The detectability of nonlinear wire line locators implementing the “oscillographic method” (AT-2, ATL, OK-1, etc.), KOM, Vizir series devices (all from Russia), etc. is 1 mW or more (the detectability of “passive measuring devices” is at least an order of magnitude or more lower). For example, the detectability of the KTL-2 device, expressed in the same units, is about 100 mW, and that of the TPU-5 device is 10-30 mW.

LBD-50 Line Analyzer (Russia)is a non-linear locator of wired communications, in which the detection ability, expressed in the same units, of 10 μW is achieved — for parallel-connected power supplies and 100 μW — for series-connected ones. In addition, the LBD-50 uses the line impedance control mode in the “idle” mode by measuring transient processes when applying a pulse signal, which makes it possible to detect parallel connections of a linear nature such as a KS circuit with a time constant of 100 μs or more. Thus, the detection ability of the LBD-50one to two orders of magnitude higher than other nonlinear locators of wire lines and at least two to three orders of magnitude higher than “passive measuring devices”.

The detection capacity of the LBD-50 for power supplies of data collection devices connected to lines is essentially the limit, since it is more practical to provide the consumed power of 10 — 100 μW using an autonomous source. Indeed, an autonomous source with a voltage of 1 V and a capacity of 0.1 Ah will provide power for such devices for a year.

In the LBD-50Standard measurement modes have been introduced, which are necessary in the process of monitoring line parameters, — leakage current of power lines and insulation resistance of lines. LBD-50 allows connection for analysis to power lines that are under voltage, in order not to trigger protection from detection of removal devices.

Analyzer LBD-50includes an auxiliary device that allows contactless quick finding of the line being inspected in a distribution cabinet, harness, etc. Search and tracking of the line being inspected is based on the supply of a test signal to the line and the reception of the magnetic field of the current flowing in it.

The set of simulators ensures the performance check of the analyzer in all modes. The cables and accessories included in the kit allow connection to the lines being inspected in almost all possible situations that arise during their inspection.

The listed capabilities of the LBD-50 analyzer allow it to be used to examine any wire communications regardless of their purpose and to detect the presence of virtually all known galvanic connections to them, including those that are fundamentally undetectable using passive “parameter meters.”

According to expert estimates, the optimal combination of equipment for monitoring wired communications in order to detect unauthorized connections to them is a combination of the most sensitive nonlinear locator and a reflectometer.

Table 1 shows the approximate costs of some domestic and foreign means of monitoring wire lines according to the proposed classification.

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