Selcom Security ST 600, Operating Manual

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COMBINED SEARCH DEVICE ST 600, OPERATING MANUAL
11
The signal is received simultaneously on both antennas and a
differential processing mode is implemented (the difference in signal levels
from both antennas is determined).
When the receiver approaches the cable, the signal level received by
the antenna located closer to the cable will be significantly higher than on
the other antenna.
When the distance from the cable to both antennas is equal (the
receiver is strictly above the cable), the signal levels will be also equal. In
this case, the difference in the values of the measured levels will be close
to zero.
The cable laid in the place where there is a "MIN" between the two
peaks (MAX) of the received test signal (on fig.8).
Fig.9 shows a diagram of the change in the level of the signal being
listened when the main unit moves with its side face to the search plane
(fig.7, direction 1).
fig.9
In this case, the maximum of the received test signal will be observed
above the cable location.