Sekotech ST-300 SPIDER, Руководство по эксплуатации, Страница: 27 / 68

OPERATING MANUAL
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For a more detailed analysis of the detected signal in the automatic mode, it can be monitored at a
set frequency. To do that, select the signal in question by moving the table cursor to the corresponding
line, and press "ENTER”.
Fig. 33 shows the display while monitoring signals at a set frequency in the automatic mode. The font
in the highlighted table line (5-7, Fig.29) will change color from white to green. The signal magnitude bar
(9, Fig.33) will change color from grey to green.
Fig.33
Actions and controls during set frequency monitoring
in the automatic mode:
“ENTER” – activate/deactivate set frequency
monitoring
– navigate the table
– receiver frequency tuning
“F1” – exit to the “SWITCH” mode (if the Electronic
Switch is connected)
“F2” – toggle modulation type (АМ/FM)
“F3” – activate the oscilloscope
“F4” – set receiver gain
“ESC” – exit to the previous screen.
2.7 “NONLINEAR JUNCTION DETECTOR” MODE
This mode serves for the detection of electronics illicitly connected to the tested cable line. The
“NONLINEAR JUNCTION DETECTOR” feature reveals both active and inactive (turned off, inoperative,
etc.) hard-wired eavesdropping devices in electric contact with the tested line, planted both within the
inspected room or facility, and beyond.
The operating principle of a wired nonlinear junction detector (such as implemented in ST300) is
in many ways similar to that of an ordinary nonlinear junction detector. Utilizing a built-in transmitter,
ST300 sends a probing signal through the tested line. The device’s receiver registers the reflected signals
at the 2nd and 3rd harmonic frequencies.
Theoretically, the absence of a response at these frequencies should mean that there are no electronics
planted on the line in question, while the presence of a response indicates that there are non-linear
anomalies. Moreover, if the response level at the 2nd harmonic frequency is higher than the 3rd, there is
a high likelihood that an electronic device is connected to the line. If, on the other hand, the level at the
3rd harmonic frequency is greater than at the 2nd, a metal-oxide-metal structure (MOM) is likely: most
probably, burnt contacts or a twisted wire connection.
In practice, one rarely gets a clear and unambiguous picture, with signals either at the 2rd or the 3rd
harmonic frequency only. As a rule, if there are nonlinear junctions, both signals will be in evidence. For
that reason, any kind of response at the 2nd and 3rd harmonics is a serious alert, no matter which signal
of the two is stronger.
The nonlinear junction detector of ST300 can be controlled both manually and automatically.
The manual NLJD mode is mostly used for testing two-wire cables, or studying the graphics on a
particular pair after a multiwire cable has been scanned in the automatic mode.
For testing multiple-wire cable, the automatic use of NLJD is advisable.
For a proper use of the nonlinear junction detector of ST300, all the telephony equipment and other
conventional electronics must be disconnected from the line to be tested.