INDEX
—– I. Ultrasonic Alarm System
II. Photoelectric Alarms
III. Passive
Infra-Red Alarms
IV. Microwave Systems
V. Word From THE RAVEN
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I.
Ultrasonic Alarm Detectors
We now move into the study of the next generation of alarms,
the area
sensors. The first area sensor component we will examine is the ultrasonic
alarm. The ultrasonic system consists of a transmitter, which emits a
frequency that lies
above the human threshold of hearing, and a receiver,
that monitors the incomming frequency.
The entire system is generally self-
contained in one unit, although occasionally on
transmitter is used with
several receivers.
The sound waves that emanate from the
transmitter follow an elliptical
(resembling an elongated oval) pattern, and ultimately return
to the
reciever. If those waves are somehow altered during their elliptical journey
the
receiver will know it, and the alarm will sound. Therefore the theory
is that if a burglar
enters a guarded area, the ultrasonic frequency will be
altered by his presence, thus alerting
the receiver to an intrusion. The
ultrasonic system is very effective, and the range is
generally about
40-50 feet.
Although ultrasonic, the frequency that these systems
trasmit is low, about
20-45 kHz (kiloHertz, or thousand cycles per second). Standard AM radio
is
between 535 and 1605 kHz. This makes detection somewhat difficult, but not
impossible. The elimination of possible ultrasound users is even easier.
People who own pets
are excluded from ultrasonic usage. Pets cause too many
false alarms, and the ultrasound may
be very irritating to them, since they
have a higher sonic perception range. Loud noises
create false alarms. Also
ultrasound cannot be employed where there is a great deal of
movement.
Blowing drapes, forced-air heating,falling boxes,Cuckoo clocks,etc. are all
causes for false alarms, and generally exclude their owners from ultasonic
club.
There
are several methods of ultrasonic detection. Multi-range bug detectors
will reveal the
presence of these alarms. Or, with the assistance of an
electronics engineer, one could make a
device that responds to frequencies
between 25 and 45kHz. Another way is to purchase a
multiband radio or scanner
that contains these low frequencies. If the frequencies are scanned
slowly,
between the aforementioned parameters, an inordinate amount of static and
interference should occur when the correct frequency is discovered. Another
way, albeit
unorthodox, is to take a mouse or a hamster near the suspected
ultrasonic sourse, and observe
their reactions. Small rodents detest
ultrasound, and they usually make every effort to avoid
it. This is the same
shit they use with those electronic pest-ridders. There are converters
available that bring the inaudible frequencies down to the human’s audio
perception
level. In the presence of ultrasound, these converters will produce
a high-pitched hum. Even
if prior detection is impossible, professional
burglars have observed that transmitters are
almost always placed in the
coner of a protected room.
Once the sensor is dectected and
located, what next? How does one penetrate
an invisible and inaudible sound barrier, in order
to disarm it, without
subjecting oneself to immediate detection? If a homeowner caused his
ultrasonic
dector to blare throughout the neighborhood,after comming home from work
every day, he would soon get many complaints from his neighbors. That is why
most ultrasonic
alarms, and most other alarms as well, have delay switches.
They allow the person to enter the
house and disarm the system befor the
alarm goes off. It allows him to arm it, and then leave
befor it begins
monitoring. This type usually has a simple on/off switch on the back, and
if
a burlar reaches it befor the thirty seconds expire, the system doesn’t know
he isn’t
the homeowner. This type is usually a desktop model, and usually has
an electrical out let
attached to it so that a lamp may be made to come on to
scare a burglar.
Because of
their simple on/off switch, these are obviously the easiest to
bypass, but there are some that
are a bit more difficult. They are often
disguised as a wall outlet, Hi-Fi speaker, book, or
are more conspicuously
located on the wall. The wall and outlet varieties are usually part of
a
larger, centralized system,and can only be reconized because Hi-Fi’s have
an even
number of speakers, and third ir fifth speaker should stand out. Also
if a speaker is just
standing there with no stero or shit to accompany it,
then thats a dead giveaway for theives.
The book type is more difficult to
locate when many books are in the room but it will be
rather thich volume
with either two twin circles or squares (transmitter and receiver) on
the
binding. The name will alos be of a generic nature.
So the burglars primary
difficulty lies in defeating the outlet and wall-
mounted types. There are several techniques
that , when used together,
enhance your success tremendously! If one has prior access to the
protected
area while the system is disarmed, sucess in defeating the system is almost
guaranteed. A burglar may lower the sensitivity to zero, fill the entire
apparatus with
aerosol styrofoam, or, if no one is around, cut through the
drywall,locate,bare,and jumper any
wires that may be found. If one does not
have prior access, he still has a few options at his
disposal.
While the owner is away one may rap the windows violently to create an alarm
and if this is done daily, the neighbors will eventually tell him that they
are tired of
blasting through the neighborhood every day. Believing his
sensitivity is too high, he will
usually lower it to compensate for the
"mysterious" outside noises. After this all
done, the burglar then wearing
a heavy oversiezed coat, or even a rug, if possible. The more
sound-absorbing
material a burglar can don, the safer he’ll be. The larger coat or rug
absorbs
rather that altar the sound frequencies, and the system’s efficiency is
compromised considerably. If the wall are covered with rugs, draperies, or
tapestries, the
effect is multiplied. But absorbing some sound is not enough,
so in addition to that the
burglar must move super-slow. If the burglar must
traverse a monitored area of twenty feet, he
may spend at least ten minutes
crossing it. The object here is to move so slowly that the
frequency remains
undisturbed by the burglar’s motion. Some ultrasonic units are hidden
behind
wallpaper or plaster, but this cuts there effectiveness by at least 25%. If
the
ultrasound units are installed in that manner, they become so unresponsive
the above methods
becomes all the more efficacious!
There is one last remote, yet viable, technique for
circumventing this type
of component. If one discovers the exact operating frequency of the
unit, he
theoretically at least, get an ultrasonic transducer of the same frequency,
and
stick it in front of the receiving unit. The whole monitored area could be
violated because
the reciever would be receiving what the transmitter was
transmitting. I’ve never tried this
befor, but it is a possibility.
II. PHOTOELECTRIC ALARMS
The photoelectric
alarm,or "electric eye" is a fairly common alarm today, and
like the ultrasonic unit
it consists of a transmitter and receiver. The
transmitter sends lightto the receiver, and if
the beam is interrupted for a
second, the reciever recognizes it and sounds the alarm. The
electric eye
princple came about during World War II so in other words the system is old!
other, or the
transmitter and the reciever may be housed together in one unit,
while utilizing a reflector
at the other end of the room. If you have no idea
what kind of alarm this is it’s the ones
that lets off a buzz when you walk
into a store. The old type of unit, which is still seen in
some places, uses
ordinary white light. These are simply defeated by shining a flashlight
into
the receiver, so that a ‘buddy’ may pass right through the beam. This is easily
detected, especially at night, because the light is plainly visible.
Even though the newer
models use invisible light, they are still terribly
easy to bypass. They are placed in front
of doors, windows,or in long hallways,
in an attempt to catch passerbys. The inherent
disadvantage of photoelectric
sensors is that they are easily seen. Although sometimes
disguised as wall
receptacles, they are almost always in plain view, and this fact alone
aids
in circumvention.
The modern electric eyes use a beam of Ultra-Violet or Infra-Red
light.
Anyone can buy from a science supply company,filters that allow them to view
UV
or IR light. The invisible light is no visible, and may be easily avoided.
Trying to shine a
beam of UV or IR light into the reciver may work but the
higher-tech models use a pulsed
beam. The receiver will be programed to the
transmitter’s frequency, and any deviation will
result in an alarm. If one has
access to the premises befiorehand, he can kick and break the
reciever, causing
it to malfunction, and causing the owner to shunt that zone before arming
the
system.
There may be cases where the componet uses laser light, instead of
Ultra-
Violet or Infra-Red. This is easily stepped over,ducked under,or otherwise
avoided,provided there is not an entire network of lasers that form an
impassable grid. This
would be only used in a very high-security situation,
but since it does occur, burglars have
discovered at least two ways which it
may be surmounted. First, a mirror system could be
designed that provides a
doorway for the burglar. The mirrors must be precisely 45* degrees,
and
since the apparatus is constructed on the spot, careful planning must go into
it
design. The viability of the next technique depends greatly on the
circumstances involved. If
there is a hiding place near the laser grid, one
can walk right through the grid and the hides
and then the burglar releases
a bird that he brought with him. After the alarm sounds the
guard will see
the bird near the alarm and wounder how it got there but will assume that it
technique may
be used used in other areas of alarm bypassing. The laser grid
system will not be encountered
very often, one of my high tech hoods say he
only came accross one at a jewlry store. So a
burglar with UV or IR filters
may be fairly certain that he is safe from detection by
photoelectric alarms.
III. PASSIVE INFRA-RED ALARMS
Passive Infra-Red
alarms, or PIRs are so called because they do not emit
Infra-Red energy, but merely detect a
change in it. A PIR probes its
monitoring area, and if any changes are detected in Infra-Red
(heat), it sounds
an alarm. A PIR records the ambient room temperature so it will notice
any
changes such as that produces by the human body. Slow temperature changes,
such as
thermostatically controlled heating systems, will not interfere with
the PIR’s duties. The PIR
is often called a thermal detector, however such
heat detectors are used primarily for fire
prevention. The PIR is immediatly
recognizable (see Fig. 1) due to its common design and
dark-red lens. They
are very common in museums,banks,and other places where high-security
is
desired.
The very fact that a PIR is passive, disallows easy detection. The
burglar
must rely solely on his observations for the recognition of a PIR system.
Due to
the nature of a PIR, they are usually placed in a very conspicuous
location, such as in the
corner of a room. The bad news for the burglar is
that PIR’s have vandal-proof germanium
lenses, are tamper-proof, and cannot
be jumpered reliably. Also the range of the PIR can be 70
feet or more,
although a PIR’s probing pattern usually only monitors an area of about 20
feet square.
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FIGURE 1. I ************ I
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THIS IS A NOT SO GOOD DIAGRAM OF A PASSIVE INFRA-RED ALARM BUT
YOU
SHOULD BE ABLE TO GET THE MESSAGE. THE DESIGN IS EASILY RECOGNIZABLE.
As reliable as
they are, PIR’s as you’ve probably guessed, are defeatable
or I wont not have wasted my damn
time telling you about them. Althogh they
are generrally undetectable, large-pet owners are
immediatly eliminated from
the list of possible PIR users. With there recent proliferation
into the
resdential market, burglars have learned to anticipate a PIR system. Some are
sold over-the-counter,although a great many are professionally installed.
Therefore, one means
of detection would be to see whether or not the alarm
company’s window decal was present.
albeit slowly
directly up to a PIR, and have not set it off. My movement was
so slow that the PIR adjusted
to the slight difference in ambient temperature
that my body was creating. Even if a PIR
system is on a silent alarm (as
disscussed in part 3), one immediatly knows whether or not he
is detected.
All modern PIR’s have a tiny red LED (light-emitting diode) that lights when
a PIR, it
took me four or five times to get it right, therefore just walking
slowly is not enough.
The greater the distance between room temperature and the temperature of the
source of
violation, the move efficiently the PIR will work. As the gap
between room temperature and the
temperature of the violator narrows, the
efficiency of the PIR decreases respectively. So
since our bodies maintain a
constant temperature of 98.6*,a PIR in a room with a temperature
around 100*
will never notice you walking through the room. Now the only problem is how
the hell is the burglar is going to heat and maintain a room above body temp.
One way is to
get to the thermostat and turn it on full blast. Another way
is to, if possible,make a hole in
the room or building, and introduce a large
space-heater. It should be at least 350,000 BTU’s
so that it can produce the
needed heat. If it blows directly into the path of the PIR unit,
the alarm
will sound. The heat must be raised gradually, or the thief defeats his own
purpose.
Mylar is a thin, metallic, plastic-like material that has a very intersting
characteristic. When worn, it allows very little body heat to escape. If a
suit, with hood,
was made of this stuff will lower the chance of detection.
IV. MICROWAVE SYSTEMS
The microwave alarm system is another transmitter/reciever motion detector,
and is
unquestionably the most difficult to successfully bypass. The system
emits a beam of
ultra-high RF (Radio Frequency) energy, generally 10.525 GHz,
and detects intruderes by
observing any change in that RF energy. Microwave
systems are extremely versatile in that one
unit may be used to monitor an
80 by 80 room or a 10 by 300 hallway.
The primary
disadvantage of a microwave system is that it has a propensity
to penetrate the boundaries of
the building it is protecting. In other words,
microwave energy that is used to guard a
business sometimes reaches out into
the parking lot, which understandably causes many false
alarms.
The detection of microwaves is actually very easy. The frequency they use,
10.526GHz, is approximately that of a poloice radar. So when you are near a
microwave alarm
system, a superheterodyne radar detector will sound. The
close resemblance between microwaves
and radar has prompted people to call
these "radar systems’" but that is technically
inaccuratte.
Once detected quite frankly there is not much one can do to bypass a micro-
wave alarm in its capacity as a simgle component. However, there are always
part of a larger,
centralized system that may be defeated. There are some
possibilities, however, for the
determined burglar, but these depend greatly
on the circumstances. For example, microwaves
will NOT penetrate metal. If
one had prior access to the building being guarded, he could
arrange metal
objects (filing cabinets,desks,etc.) so that he could reach his destination
Microwaves systems
cannot detect movement if it proceeds at less than two
inches per second. That is indeed slow!
When a burglar encounters a miicro-
wave alarm he is expected to silence the annunciator (see
part 3).
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