BASIC OPERATIONS
64
Fig.56
Existence of indication on a "blue" scale means that in the tested pair it is detected by MOM-
structure.
Sometimes the response at the frequency of the third harmonic can be given by eavesdropping
devices. In any case, if there are signals displayed on the "red" and "blue" scales (regardless of
the ratio of their levels), further testing of the pair of wires on which the nonlinearity was
detected is necessary.
Test results for various types of connections of eavesdropping devices to the tested cable
In Fig.57 the result of testing of a telephone cable is presented, at
parallel connection to
wires #4 and #5
(the central pair of a cable).
The telephone radio transmitter, the high-frequency wire transmitter, the dictation adapter can
be such devices. Level of the second harmonic exceeds the level of the third that speaks about
connection of the electronic device.
Fig.57
In Fig.58 the result of testing of a telephone line is presented,
at parallel connection of the
electronic device to wires #3 and #6
(the electret cable microphone using non-used two
wires or the high-frequency wire transmitter for information transfer). Level of the second
harmonic exceeds the level of the third (the electronic device connected to the cable).
