OPERATING MANUAL
34
ST 401 ‘CAYMAN’ NLJD
35
Items known to contain semiconductor components (electronic instruments, office and home
equipment, communication devices, etc.) are checked by other means.
When running checks on enclosing structures, it is important to set a suitable receiver gain. If
excessive, it may well cause detection of objects behind the walls, which may be a problem when
there is no access into the adjoining spaces. On the other hand, if the gain is too small, targets of
interest with a weak response may remain undiscovered in the structure under scrutiny.
While scanning walls and other large vertical structures, it is recommendable to move the
antenna from top to bottom in a serpentine fashion, as is shown in Fig. 9.
Fig. 9
The antenna head should be held at a distance of 5-15 cm from the surface.
If a potent response is registered (all LEDs in an multi-segment gauge light up), the gain
should be decreased in order to establish the exact location of the responding target.
The primary task for an NLJD is the discovery of eavesdropping devices, whose giveaways
are the signals returned by semiconductor-containing electronic components and by MOM-
structures on casings, at junctures, etc. Therefore, particular attention should be paid to scanned
areas where responses have been observed on the red multi-segment gauge alone, and on both
red and blue multi-segment gauges. The nature of each such response should be determined and
its source identified.
A strong, off-scale response on one of the multi-segment gauges may be accompanied by a
much weaker one on another. As a rule, the former is a true response and the latter a false one; it
is advisable to decrease the gain or move away from the target until the readings stop going off
the scale.
Small-sized objects should be checked at locations where no response is observed on any of
the three multi-segment gauges, preferably away from large metal structures, pillars, cabinets,
safes, etc.
Switching to other modes
Other modes are accessible from this mode:
• AUTO mode (press MODE)
• AUDIO mode (press AUDIO)
• adaptive self-tuning mode (press and hold MODE)
2.5. Automatic Gain Control
In addition to the manual mode,
ST 401 ‘Cayman’
has an automatic gain control mode:
depending on the level of the incoming signal, the receiver gain is automatically adjusted so as
to prevent the indicators going off scale. This facilitates the operator’s work to a degree, as well
as reduces the chance of false triggering. However, the detection range in this mode is decreased,
and there is a higher risk that a threat should remain unnoticed.
To change from manual to automatic gain control, press MODE. The MANUAL indicator
will go out and AUTO will light up. The SENS gain indicator is inoperative in this mode.
Switching to other modes
Other modes are accessible from this mode:
• MANUAL mode (press MODE)
• AUDIO mode (press AUDIO)
• adaptive mode (press and hold MODE)
2.6. Listening (AUDIO mode)
The AUDIO mode is primarily intended for analysing target responses by listening to the
demodulated signal output. This should give the operator ample information to identify the target
type.
To switch to the audio mode from either search mode, press AUDIO. The AUDIO indicator
will light up on the antenna head (Fig. 4: 9). The device status will be displayed on the antenna
module as described in
Table 2
below.
Table 2
legend
colour
light indication
meaning
DC
red
continuous
The antenna module is powered properly.
blinking
The battery is discharged and needs to be
replaced.
CH
yellow
continuous
The 5-segment bar displays the selected
probing frequency combination
(see
Table 3
).
AUDIO
yellow
continuous
AUDIO mode off/on indicator
LEVEL 3
white
varying numbers of
lit LEDs
The 16-segment bar displays the levels of
returned signals.
