Sekotech ST-300 SPIDER, Руководство по эксплуатации, Страница: 51 / 68

OPERATING MANUAL
49
Readings on the blue bar graph, that indicate the presence of MOM-diodes, may be brought
about by oxidation of contacts in the socket, twisted connections, etc. However, one should take
such readings seriously, as eavesdropping devices may have elements that yield a response at
the third harmonic frequency of the test pulse (e.g., anti-parallel diode connections).
Therefore, if the red and blue bar graphs show any responses at all, quite regardless of their
relative magnitudes, one should analyze the current pair of wires further.
If open-circuit testing has shown nothing on either red or blue bar graph, this means that no
electronics in parallel connection to the line have been discovered. Now the wire pair should be
short-circuited and tested for series connections.
Keeping the main screen of the “NLJD” mode on, short-circuit the tested wire pair at the opposite end
with the Short-Circuiting Socket (23, Fig.1).
If there are readings on the red and/or blue bar graphs, there is a series connection of a non-
linear element to the wire pair.
3.5.2. Nonlinear Junction Detector of ST300 in Use: Automatic Mode
The automatic “NLJD” mode is used for testing multiple-wire cables.
EXAMPLE
For illustration purposes, let us assume that a multiple-wire cable consisting of four twisted pairs is
being tested. As unsolicited connections can be both parallel and series, the line should be tested in both
open-circuit and short-circuit modes.
The cable in question is plugged into a 8P8C socket, and equipped with a 8P8C plug at the other end.
The line is kept as a spare, not connected to any known equipment.
PROCEDURE
Connect the Electronic Switch to the Main Unit of ST300 (1.3.3).
Connect the line to be tested to the Electronic Switch (6А, 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. 49 (1).
Exit the “CABLE SETTINGS” to the main screen of the “NLJD” mode (button “FUNC” or “ESC”).
Activate the automatic mode (“MODE” button). A table will appear on the screen.
Launch scanning (“F4” button).
Having run the full cycle of testing all the two-wire combinations, scanning will stop. The table
will have filled in with graphic data on reflection responses at the second and third harmonic
frequencies of the test pulse, for each wire pair. Thus, the operator will get a full picture as
to the presence of nonlinearities throughout all the two-wire combinations, as well as relative
levels of response at the second and third harmonics.
If a response on any pair is too strong (one of the graphs goes off scale), the power of the
probing signal should be reduced. To do that, highlight the wire pair, go to the main screen of
the “NLJD” mode (“MODE” button) and, using the key, reduce the test pulse magnitude.
Press “MODE” to return to the automatic mode.