OPERATION
79
audio as received by the microphone on the OSCOR. The graph labeled “Demod” is the demodulated
audio from the currently tuned signal.
Note: Ideally, for an accurate correlation determination, the most prominent sound source heard by the
OSCOR unit should also be the most prominent sound heard by the bug. It may be advantageous to
have an easily perceptible, non-periodic sound source in the room; music or conversation in an
otherwise silent room should work well. It may also be beneficial to walk around the room with the
OSCOR unit to increase the chances of both the OSCOR and the bug hearing the same ambient
noise. The fan noise from the unit, although it may be almost imperceptible as far as ambient noise is
concerned, will be very significant to the OSCOR’s speakers. This should be taken into account when
checking for correlation.
Warning: If the OSCOR determines that there is no correlation between demodulated audio & ambient
room noise, it does not necessarily mean that the signal is not a threat; it only means that the signal
does not acoustically correlate with the selected form of demodulation. Signals that are digitally
modulated, spread spectrum, frequency hopping, or contain video content will not correlate. To locate
the source of these types of signals, you will need to use other methods, such as RSSI level (see page 76)
or RF mapping, a process taught in REI’s TSCM training classes. Contact REI (
sales@reiusa.net
) for
training dates.
Ranging
The ranging function uses a sound source and the speed of sound to calculate the range of a correlated
signal.
For the most accurate ranging information, the OSCOR unit features a white noise generator, which is
used for the sound source. However, it is important to note that this may alert others to your counter
surveillance activities.
Note: If during the correlation phase, headphones were used to listen to demodulated audio, it will be
necessary to unplug the headphones from the OSCOR unit during the ranging phase. The white noise
generated by the OSCOR needs to be picked up by the unit’s internal microphone and by the potential
eavesdropping device. For this to occur there can be no headphones plugged into the headphone jack
on the OSCOR unit, so that the white noise is heard from the OSCOR unit’s built-in speakers.
To use the ranging function:
1.
If during the correlation phase described above, a demodulated signal correlates with room
audio, the OSCOR unit is able to determine the distance, or range, from the OSCOR to the
listening device. To determine this distance, select the
Ranging
icon from the Corr | Range
submenu. Note: The
Ranging
icon cannot be selected unless the
Correlate
icon is highlighted.
2.
If the audio of the OSCOR unit is currently muted, you will be presented with a dialog box asking
if you wish to unmute for ranging. Select
OK
or press
F5
to unmute the audio and use white
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