BASIC OPERATIONS
61
5. Select the cable type - "LOW-CURRENT LINE" ("Low Voltage" item in menu)
6. Select the frequency range (100 kHz - 60 MHz or 100 kHz - 180 MHz).
7. The Switch table will be displayed on the screen, in which all combinations of wire pairs are
displayed
8. Press "FUNC" and set cable type ("non twisted" type, wires #3,4,5,6).
When connecting a four-wire telephone cable, contacts ##3, 4, 5, 6 of the Switch slot are
used. Based on this, it is necessary to test the combinations of wires:
3-4; 3-5; 3-6;
4-5; 4-6;
5-6.
It is necessary to consider that the transmitter can be powered normally (from the activated
"4-5" pair), and transmit information over another pair.
9. In the Switch table, set the cursor on the row corresponding to the pair "3-4". The cell displays
the voltage value in the connected pair (during normal operation of the telephone line there is no
voltage on this pair).
10. Press "ENTER". The spectrogram of the "3-4" pair will be displayed on the screen.
11. Set optimum gain ("F4").
12. Turn on the AUTOMATED mode ("F2").
13. Listen to all detected signals consistently switching AM and FM demodulators ("F2").
14. Exit the AUTOMATED mode ("ESC") to the PANORAMA mode.
15. Press "F1" for switching to the Switch table (SWITCH CONTROL mode).
16. Set the tabular cursor on the next pair of wires, press "ENTER".
17. Test the remaining combinations of wires in accordance with item #11-14.
Listening of PTS sound means existence in the room of the active analog wire high-frequency
transmitter.
In this case (remaining on that combination on which "the dangerous signal" was detected) it
is necessary to disconnect the telephone set from the cable under test.
If at the same time the "dangerous" signal is gone, so the source of this signal is installed in
the telephone set.
If at shutdown of the telephone set the signal is not gone, so its source is connected to the
cable (indoors since there is a correlation with a control sound).
Also it is necessary to pay attention to digital signals which are not correlated with a control
sound.
Perhaps these signals are transmitted by an encoded (digital) transmitter. It is recommended
to analyze such signals in the OSCILLOSCOPE.
The algorithm of localization of microphones is described in
7.2.3. FEATURES OF TESTING OF THE HF TELEVISION CABLES
On the television cables high frequency transmitters of audio signals and/or digital or analog
transmitters of video signals can be installed.
In this case, the cables are used as a channel for transmitting audio and video information.
The technical capabilities of ST 301 do not allow demodulating the video signal.
