Sekotech ST-300 SPIDER, Руководство по эксплуатации, Страница: 50 / 68

ST300 SPIDER
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For the detection of parallel-connected devices, the line must be open-circuited at the far end. For the
detection of series-connected devices, the line must be short-circuited.
Two-wire cables are best tested in the manual “NLJD” mode.
Multiple-wire cables are best tested in the automatic “NLJD” mode.
3.5.1. Nonlinear Junction Detector of ST300 in Use: Manual Mode
The manual mode is typically used in two situations:
– for testing a specific pair of wires where the suspect signal has been discovered while checking a
multiple-wire cable;
– for testing a two-wire cable.
EXAMPLE
Let us illustrate the procedure assuming a two-wire analogue telephone line of an office PBX is to be
tested. Further assumptions are the following:
The two central contacts of a 6P2C plug are in use. The eavesdropping device may be connected in
either series or parallel configuration.
A telephone device is connected to the line through a socket (with the phone receiver “on the
hook”). The line is power-fed from the PBX and operates normally.
PROCEDURE
Disconnect the line to be tested from the PBX.
Disconnect the telephone from the line.
Connect the Electronic Switch to the Main Unit of ST300 (1.3.3).
Connect the line to be tested to the Electronic Switch (6B, Fig.47).
Turn on ST300 and go to the Start Menu (2.1 – 2.2).
Go to the main screen of the “NLJD” mode (“F2” button).
Activate the “CABLE SETTINGS” mode (“FUNC” button).
Set the cable parameters (2.5.1.1) as shown in Fig. 50(3).
Exit the “CABLE SETTINGS” mode to the main screen of the “NLJD” mode (button “FUNC” or “ESC”).
Go to the main screen of the “SWITCH” mode (“F1” button).
On the main screen of the “SWITCH” mode, set the wire pair “4” – “5” (2.4.1.1).
Exit the “SWITCH” mode to the main screen of the “NLJD” mode (“F3” button).
The screen will show the results of testing the active wire pair (“4”–“5”) for nonlinearities in the
open-circuited configuration.
The testing results are represented in the form of three horizontal bars, of which
– the upper bar graph (white) shows the reflection signal magnitude at the frequency of the test
pulse; the readings are proportional to the resistance on the tested wire pair;
– the middle bar graph (red) shows the reflection magnitude at the second harmonic frequency
of the test pulse (indicative of semiconductor content);
– the lower bar graph (blue) shows the reflection magnitude at the third harmonic frequency of
the test pulse (indicative of metal-oxide-metal structures).
When no devices are connected to the tested pair of wires, there should be no readings on any
of the three bars.
Therefore, readings on the red bar graph will indicate that there is electronics attached to the
tested wire pair.