3. Alarm Warranty
AlarmWarranties on a policy generally
require that the burglar alarm is :
A) Properly maintained
B) Armed (on) when the premises are
unoccupied.
The term ‘activated’ is in respect of the alarm
being triggered during illegal intrusion.
On this basis, the Insured is given the benefit
of a premium discount.
5. BASIC COMPONENTS
The Brain
Control Panel
The Nervous System
Magnetic switches
Glass break detectors
The “EYES”
Passive Infra Red Detectors (PIRD’s)
The Mouth
Radio transmitter or tele-communicator
10. Magnetic alarm switches are
connected in a loop, which are
always closed (always in contact).
They consist of electric contact
switches and magnets. When a
door or window is closed, the
switches sensitive to magnets
close the circuit and when they
open, breaks the contact thus
cutting the circuit.This sets off the
alarm. End of line resistors are
necessary to prevent effective
tampering.
12. The original method used to protect glass required the
application of a conductive metallic tape (foil), directly to the
glass. The foil was varnished onto the glass 4-5 centimetres
from the edge and glued around the perimeter of the glass. If
the glass was broken, the cracks would cause the foil to break.
While this was apparently a reliable method of detecting glass
breakage, it was very labour intensive to install and prone to
extensive service repairs from scratches and breaks in the foil.
Today almost all glass break sensors are acoustic devices,
although vibration detectors are still being used. There are
many advantages to using acoustic detectors. They are visually
attractive, less expensive to install and maintain. It is said that
current detectors are very good at tripping to only the sound of
breaking glass and that ‘new’ glass break units are less prone
to false alarms.
13. The ‘eyes’ – Passive Infra Red
The most misunderstood alarm device
14. Is a Passive Infra
Red Detector a
motion sensor , or
is it a heat
detector?
16. A Passive InfraRed sensor / detector (PIR sensor /
detector) is an electronic device that measures
infrared (IR) light radiating from objects in its field
of view. PIR sensors are often used in the
construction of PIR-based heat detectors, often
confused for motion detectors. Apparent motion is
detected when an infrared source with one
temperature, such as a human, passes in front of
an infrared source with another temperature, such
as a wall.
17. All objects emit what is known as black body radiation. It is
usually infrared radiation that is invisible to the human eye
but can be detected by electronic devices designed for such
a purpose. The term passive in this instance means that the
PIR device does not emit an infrared beam but merely
passively accepts incoming infrared radiation. “Infra”
meaning below our ability to detect it visually, and “Red”
because this colour represents the lowest energy level that
our eyes can sense before it becomes invisible.
Thus, infrared means below the energy level of the colour
red, and applies to many sources of invisible energy.
18. Infrared (IR) light is electromagnetic radiation with a
wavelength between 0.7 and 300 micrometres, which
equates to a frequency range between approximately 1
and 430THz.
IR wavelengths are longer than that of visible light, but
shorter than that of terahertz radiation microwaves.
Bright sunlight provides an irradiance of just over
1 kilowatt per square meter at sea level. Of this energy,
527 watts is infrared radiation, 445 watts is visible light,
and 32 watts is ultraviolet radiation.
Therefore, bright sunlight, being the main source of
infrared light, effectively and literally ‘blinds’ external
passive infrared detectors, as well as internal detectors
that face into strong sunlight shining through windows.
19.
20.
21.
22.
23.
24. It is no more a motion sensor than torch is an
X-ray device. It gives the impression it is a
motion sensor because it more often than not
activates when there is apparent motion.
Except when the item moving is at the same
temperature as the room, or, the heat of the
room exceeds the operating temperature of
the device.
28. South African Intruder
Detection Services Association
SAIDSA
By-law 5 and 25:
Location and enclosure
Where ceiling access is possible, the control
panel, radio and antenna shall be installed a
minimum of 1.5m below the ceiling, in an area
protected by a volumetric detector on an instant
zone not visible from outside. The door of the
control panel must be tamper proofed on a 24
hour zone. (July 2003)
36. A PIRD is a heat sensor……
On the installation instruction insert, the
maximum operating temperature is listed,
usually between 40°C to 50°C. The human
body is measured at 37.98°C.The PIRD
cannot detect something that is colder than
itself.
What is the average temperature inside a roof
cavity of a house in Durban in December?
Can a PIRD see through roof trusses?
39. Active infrared is when infrared light is
emitted and then detected when it bounces
back off a surface. Passive infrared is the
infrared given off naturally from the surface
of a material.
The difference….
40. The Power Source
The battery is the single most important component of the
burglar alarm system.The system is totally dependent on
the correct power being delivered to all its components at
all times.Too little power causes an unstable system, false
alarms or non-activations.Too much power, on the other
hand will reduce the lifetime of the battery or destroy it.
No power means that the system is running off the battery
that is no longer charging.This is fine in the short term,
providing that the battery in question is still 100% efficient.
Frequent power cuts, for whatever reason, have a
detrimental effect on an alarm battery by reducing its
lifetime bit by bit.
41. Many lower quality Sealed Lead Acid batteries, when
fully discharged, do not always recover from a total
discharge.This in effect means that thousands of
burglar alarm systems in South Africa are literally
running off their transformers, particularly in older
systems.
A good quality Sealed battery should supply a
minimum of 6 hours in a standby condition.
Hence a reason for an alarm warranty insisting that
the system is properly maintained.
42. Like PIRD’s, Sealed LeadAcid and Gel batteries do not like heat.
They will ensure optimum capacity at around 20°C to provide a
lifetime of between five and seven years under normal
conditions.The battery life is approximately halved for each 10°C
above normal temperature.
If an alarm battery is installed in an area that reaches 60°C. or
higher, the lifetime can be reduced to as little as 5 months. In fact,
the temperatures in a home that has a tin roof can reach well into
the 80’s when the outside temperature is 35°C.
Many installers install the main panel and battery in the roof!
43. Pet Alleys…
Although great strides have been made in detector technology,
we have yet to see a totally fool proof pet “immune” detector
that does not compromise the catch performance of the
detector.
A cat or small dog may look the size of a human if it gets close
enough to the detector. In fact, at close range, a cat may be seen
as the size of a tiger.
Most pet “friendly” detectors will not detect pets, provided the
pet stays on the floor.
44. Memory…………
All alarm control panels are basically
computer ‘mother boards’.
With one or two exceptions of the older
models, all have built in ‘buffer’ memories.
The memory can normally hold up to 1000
events.
There is therefore no excuse for the average
Insured not being able to prove his alarm was
armed / on at the time of an intrusion.
