(Part-1
1. Introduction
This
topic is designed to cover basic concepts and principles that address
the security-related and environmental issues requiring security
systems.
2. Learning Objective
After completing this topic, a person should be able to:
2. Learning Objective
After completing this topic, a person should be able to:
- Compare the traditional definition of assets protection with today's definition of security assets protection;
- Describe the importance of people, material, and property as they relate to security assets protection;
- Describe the purpose of an Assets Protection Program (APP);
- Identify sources of potential disruption to operations, both internal and external;
- Discuss the five (5) objectives of an APP;
- Describe the significance of countermeasures and management support within an APP;
- Explain how vulnerability analysis, countermeasures, and operational testing work together in an APP and describe their outcomes.
3. Assets Protection
In the past "security" was fairly straight-forward. Images of bank guards or fences topped with barbed wire accurately represented the extent of security solutions in most instances. That was yesterday.
Today, the demands placed on security professionals have moved far beyond guards and barriers. Effective security requires a comprehensive "systems" approach that protects all assets of a company. In this section, you will learn:
Throughout this series I will refer to the "company." In most instances, however, these discussions also apply to many different types of organizations. These may include colleges and universities, medical facilities, industrial plants, etc. Corporate security applies to these settings as well.
4. Defining Assets
In general, a company's assets may be divided into three (3) main areas.
These include:
In the past "security" was fairly straight-forward. Images of bank guards or fences topped with barbed wire accurately represented the extent of security solutions in most instances. That was yesterday.
Today, the demands placed on security professionals have moved far beyond guards and barriers. Effective security requires a comprehensive "systems" approach that protects all assets of a company. In this section, you will learn:
- What these assets include?
- What the security issues are regarding each asset category, and
- What security solutions are available to protect them?
Throughout this series I will refer to the "company." In most instances, however, these discussions also apply to many different types of organizations. These may include colleges and universities, medical facilities, industrial plants, etc. Corporate security applies to these settings as well.
4. Defining Assets
In general, a company's assets may be divided into three (3) main areas.
These include:
- People - Employees, customers, and others who may visit a site
- Materials - any materials used in a company's processes
- Property - both physical and intellectual

It is often said that people are a company's most important asset. A company's employees, after all, are responsible for coming up with the ideas for goods or services which bring success to an enterprise. Employees design, engineer and manufacture the product. They manage these operations, track costs and revenues, and provide a sense of overall direction for the business. All of these individuals are valuable assets to a company.
In addition, customers, contractors, vendors, and other visitors become part of a company's assets, particularly while they are within the company's physical plant.
People can also be potential threats or liabilities to a company. Both outside individuals and company personnel who may be intent on injuring the company in some way — by theft of materials, for example — present significant concerns to security operations. Example of such "people" threats include:
- Protesters/demonstrators
- Thieves
- A disgruntled employee damaging property or interrupting operations

6. Materials
Consider all the materials typically used by a company. The raw material used in a company's processes must be protected from theft, damage, or any other problems which would interfere with manufacturing. Finished products are also part of the company's material assets and should be a major security concern. In addition, any materials which may be created as by-products of the manufacturing process are also of concern. Some of these materials (e.g., chemicals, gases, lubricants and fuels) may be classified as hazardous materials and present a special security concern.
Consider all the materials typically used by a company. The raw material used in a company's processes must be protected from theft, damage, or any other problems which would interfere with manufacturing. Finished products are also part of the company's material assets and should be a major security concern. In addition, any materials which may be created as by-products of the manufacturing process are also of concern. Some of these materials (e.g., chemicals, gases, lubricants and fuels) may be classified as hazardous materials and present a special security concern.

7. Property
Traditional approaches to security have always focused on property, but today property includes much more than just physical items, and this, of course, impacts corporate security concerns. Physical property is clearly an asset; therefore, it requires a plan to protect it. However, there is a whole range of other types of property, generally described as intellectual property. This can include:
Traditional approaches to security have always focused on property, but today property includes much more than just physical items, and this, of course, impacts corporate security concerns. Physical property is clearly an asset; therefore, it requires a plan to protect it. However, there is a whole range of other types of property, generally described as intellectual property. This can include:
- Research
- Computer programs created by the company
- Operational procedures
- Marketing and sales data
- Certain company policies

(Part- 2)
1. Introduction
Today,
I will discuss one of the security basics named “Physical Security
Concepts”. It covers issues related to Physical Security as a key
component of a comprehensive organizational approach to security. In my
last article (Part-1) I have discussed Design consideration of physical security and barrier.
2. The Three Layers of Barrier Protection
The
outer protective layer may consist of fencing, natural barriers,
lighting systems, signs, and alarm systems. These controls generally
accomplish two related functions:
- Defining property lines
- Channeling personnel and vehicles through designated access points.
The
middle layer of barrier protection is usually considered to begin at
the exteriors of any buildings on the site. Features may include:
- Lighting systems
- Alarm systems
- Locking devices
- Bars or grill work
- Signs
- Additional fencing.
More
positive controls are used at this level than at the outer layer.
Ideally, those planning security for a site must consider each building
to be a six-sided box. Barrier design, therefore, should include
provisions for protection from roof entry as well as intrusion from
underground.
The
inner lay may itself consist of several levels. This inner and final
barrier against intrusion will ensure that an intruder (any person
attempting to enter a region who at any given moment may not be
authorized to do so) will be detected even if the outer and middle
layers of protection have failed to do so. Items or areas that could be
protected are research/production data, equipment necessary to conduct
operations, sensitive/competitive processes, negotiable instruments,
critical organizational records, computer rooms, etc.
The
security design of the inner barrier layer also prevents the intruder
from accessing anything deemed to have value. Features may include:
- Window/door bars
- Locking devices
- Barriers, signs
- Access/intrusion/alarm systems
- Communication systems
- Lighting systems
- Safes and controlled areas

3. Types of Barriers: Natural, Structural, Human
Effective barriers need not be necessarily man-made. Barriers against intrusion may be naturally occurring, man-made, or human.
Natural barriers should be considered as part of a security plan. Natural barriers include:
- Bodies of water, including rivers, creeks and lakes
- Woods
- Cliffs
- Wild hedge plant
In addition to being effective outer layer barriers, natural barriers can be quite cost effective.
Structural
barriers are man-made (or natural barriers manipulated by security
designers). They are placed at strategic locations around a site to
control access. Structural barriers include:
- Berms - man-made hillocks
- Retention ponds
- Planted tree lines to define boundaries
- Walls
- Fences
- Doors, gates, and locking mechanisms
- Ditches
- Posts
- Bollards - stanchions controlling traffic flow
- Glazing materials.
The
third type of barrier comes in the form of a human presence. Here the
security design uses people to control access and limit movement areas.
Human barriers may be in use in any of the three layers of barrier
protection. Personnel used to provide human barriers include:
- Public safety/police
- Contract/proprietary security officers
- Receptionists.

4. Preventing Interruption of Operations
For
many organizations, it is not enough to keep unauthorized personnel out
of secure areas. More is required. If operations are interrupted, the
results can have a serious negative impact on the organization, its
employees, the people it serves, and the community of which it is a
part. Because of the importance of maintaining normal operations,
minimizing the potential interruption of operations is the second major
goal of an in-depth physical security plan. When thinking about
interruptions to operations, sabotage and vandalism are certainly
important security considerations; however, such interruptions can also
be caused by natural disasters, environmental disasters, or industrial
accidents.
A
well-designed Physical Security plan must incorporate policies and
procedures to ensure continued operations even should one of the above
situations occur. A comprehensive approach to Physical Security must
include disaster recovery plans. Such plans must include:
- Evacuation procedures
- Marshaling of resources to deal with the emergency event
- Maintaining order on the site
- Administering first aid and directing emergency services and operations
- The protection of assets (personnel and property).
The
presence on-site of hazardous materials adds to the challenges and
complexity of a disaster recovery plan. An event involving such
materials may require highly specialized response utilizing equipment
and personnel far beyond the scope of non-Haz Mat events. Plans designed
in response to potential hazardous material incidents must be developed
with local and possibly even national public safety assistance, being
sure to meet country environmental safety regulations. The plan must
address issues such as:
- Relocation of materials
- Containing spills
- Minimizing losses and contamination of personnel and property
- Notification to proper authorities and employees
- Securing affected areas to prevent unauthorized entry.

5. Perception as Protection
Clearly
a major goal of any physical security plan is to ensure employees,
customers, visitors and vendors are secure. In reality, accomplishing
this goal requires security planners to look beyond the arrangement of
barriers, the institution of access control, etc. Security personnel may
know all prudent and expedient measures have been taken to ensure a
high level of security. If, however, workers, customers, and others do
not feel secure, then even the best efforts of the security department
will have failed.
For
a security plan to be truly effective, employees, customers, visitors
and vendors must perceive they are secure; they must believe they are in
a safe and secure environment. Consider the effect of a simple
homeowner security device — a sign that read, "Beware of the Dog." You
do not need to see the dog for it to have an effect. Designers of an
effective security plan must recognize the key role "perception" plays
in providing protection — and not just from the point of view of
authorized personnel at a site, but from the viewpoint of potential
intruders as well.
First,
to incorporate elements in a security plan which will ensure a
"perception of security," planners should begin by identifying factors
and security issues that concern persons at work and visiting the site.
What fears do these persons have and what are reasons for these fears?
Next,
a physical security plan must involve all groups within an
organization. From the start, security must be viewed by all as part of
every employee's responsibility. All personnel must understand that they
play an important role in the organization's security program.
Every
element of the Physical Security Plan should be reviewed not only for
its ability to reduce unauthorized entry and loss prevention but also
its ability to create the perception of a safe and secure environment.
To restate this, effective security protection consists not only of the
actual measure taken, but also the perception of protection it presents.
For example, a studies have shown fencing topped with barbed wire can
be breached by knowledgeable intruders in under ten seconds. For many
people, however, this same fence may appear impossible or difficult to
breach, and therefore will provide an initial deterrence.
In
many organizations, including retail store operations, security
programs can be enhanced by the use of devices, such as signs and dummy
CCTV cameras (e.g., the mirrored half-dome CCTV enclosure) to create or
heighten the illusion of protection. An individual only has to see the
dome — not any camera which may be inside it — to understand he or she
may be under surveillance.
In summary, effective protection schemes must incorporate three approaches to security:
- Visible with real protection
- Not visible with real protection
- Presenting the appearance of protection but in fact an illusion.

I have to finish here. In the following articles, I will provide more detail in designing such a protection plan.
(Part-3)
1. Introduction
In my last two discussions (Part-1) and (Part-2),
I have discussed Design consideration of physical security, Barriers,
Layers of barriers, Type of Barriers and perception of protection.
Today, I will discuss the Protection Scheme Guidelines as below:
1.1 Protection Scheme Guidelines
1.2 Guidelines for Illusory Techniques
1.3 An Essential Ingredient: Incident Response
1.4 Cost Impact on Security Plans
1.5 Guidelines for Protective Lighting
1.6 Object/Area Illumination
1.7 Lighting as a Physical Deterrent
1.8 Lighting as a Psychological Deterrent
1.9 Security Lighting Standards
2. Protection Scheme Guidelines
Developing
an effective Physical Security plan involves a series of logical steps.
While the specific content developed during these steps varies from
organization to organization, the basic steps remain the same. The first
step is to perform a "Vulnerability Assessment." (This process was
discussed in "Security Principles and Operation-Part 3".)
Based on this assessment, as developed for a particular organization,
security planners can identify specific "protection objectives" for the
organization. At this point, planners can determine what techniques and
equipment will be required to accomplish the objectives. Included in
this step is a determination of which objectives may be supported with
illusory techniques.

3. Guidelines for Illusory Techniques
Establishing
the image of security requires an assessment of what types of illusions
might be utilized and how they will relate to the tangible security
assets of the program.
One
word of caution, regarding illusory techniques: occasional failures of
illusory techniques occur — as in shoplifting in a department store's
ready-to-wear department. It may be that some loss is acceptable in such
a store's security plan for that department. Now consider the same
department store, but this time the jewelry department. Here any loss is
deemed unacceptable. Armed with these two pieces of information, the
security designers for the store can plan an appropriate security
response to the potential threats. In the case of the ready-to-wear
department, it may be that the use of simulated CCTV domes is
appropriate. On the other hand, when it comes to the jewelry department,
the same planners may call for a series of domes actually containing
functioning CCTV surveillance cameras. At each location, appropriate
signage warning of surveillance may further deter potential threats.
Clearly in this setting, a variety of security options is appropriate.
Therefore, real techniques (CCTV, alarm systems, and signage) in
combination with illusory techniques (simulated CCTV domes) is deemed to
provide effective levels of protection.
When
these techniques are combined with procedures such as selected
prosecution of violators, the organization — in this case the store —
can create a comprehensive and effective security plan.
A
note of caution: once an illusory technique has been compromised, it
has no further value and should be immediately discontinued. In order to
prevent this from occurring, it is essential to keep the actual number
of personnel who know the true aspects of the security plan to the
absolute minimum.

4. An Essential Ingredient: Incident Response
A
key component to ensuring the on-going effectiveness of a security plan
is the consistent and predictable response to any incidents that may
occur. The security plan, therefore, should have clearly defined
responses in place in the event of an incident. Such responses should be
balanced in their effect. They must be designed to be both preventative
(discouraging attempted threats) and punitive (punishing the current
offender).
A
preventative response is initiated before the unauthorized person
reaches the protected objective. It is designed primarily to be a clear
warning that additional response capabilities are in place. As such a
preventative response is intended to discourage continued attempts and
to turn away the intruder.
A
punitive response is initiated once the penetration has occurred or is
still in progress. Rather than turning away an intruder, the objective
of punitive responses is the identification and apprehension of the
perpetrator. An example of a punitive response is the capture of a
robber resulting from a police response to a silent alarm from a bank.
Balanced
response it the preferred methodology and involves both of the previous
responses used singularly or in combination throughout the security
plan.

5. Cost Impact on Security Plans
A
final consideration in a protection scheme is financial: available
funds versus costs. Obviously sufficient funding must be available to
provide adequate protection based upon the risk management profile.
Funds must be sufficient to cover costs associated with personnel,
training, equipment, and maintenance requirements. The cost of the
system must be viewed in contrast to the potential cost of losses
resulting from inadequate security measures. This kind of analysis can
be an important aid as decisions are made regarding funding levels for
an organization's security plan.

6. Guidelines for Protective Lighting
An
important component of a comprehensive security plan is lighting.
Security Protective Lighting has three functional objectives:
6.1 To illuminate a person, object, place or condition of security to permit observation and identification
6.2 To be a physical deterrent through the glare effect of direct light on the human eye
6.3
To be a psychological deterrent creating in an intruder's mind the
awareness that he or she will be discovered and observed during any
unauthorized entry attempt.

7. Object/Area Illumination
The
most obvious reason for protective lighting is to make certain any
person, object, place or condition will be sufficiently illuminated to
provide effective security in a given region. In order to assure
sufficient illumination a number of conditions must be met. For example,
lighting designers must consider natural properties of reflectance,
light absorption capacity, mobility and an object's inherent sensitivity
to light. All these factors affect an entity's visibility. Other
factors to consider include:
7.1
The schedule of observation. Will the observation be constant or
intermittent? If intermittent what will the frequency of observation be
and will the observation be performed on a regular or random basis
7.2
The means of observation. Will the observation be performed by a person
or CCTV system? In either case, sufficient illumination must be
available to accomplish the observation. For CCTV, the camera
specifications will list required illumination.
7.3
The area and quality of coverage. Is it necessary to observe all
details in the area of coverage, or will only selected elements within
the area be of interest? What level of detail is necessary? Is it
necessary, for example, to observe changes in color? This clearly would
affect decisions regarding the "quality" of the illumination, in this
case color temperature, specifically.
7.4
Reliability of the illumination devices. If, for example, observation
is to be constant, equipment mean time between failure rates as well as
back-up power source must be considered. In addition, system designers
must factor in restoration time of illuminating devices when a power
failure occurs. Some lamps require several minutes of operation before
they reach their specified levels of illumination output and quality.
When
considering an illumination system for protection, the answers to these
questions are essential in implementing a system which meets the
organization's requirements.

8. Lighting as a Physical Deterrent
In
addition to providing simple illumination in an area of coverage,
protective lighting may be given a more "active" role in deterring
intrusion. One factor in the effectiveness of lighting used in this
manner is it's brightness and position in relation to the intruder.
Earlier I referred to this as the "glare effect." Consider the
disorienting effect (and therefore deterring effect) of suddenly filling
an area with high levels of illumination triggered by an intrusion
detection device. If this is a component of a lighting system design,
note that such an effect may be enhanced by keeping an area in low light
levels until an intruder is detected.
When protective lighting will be used as a physical deterrence, the following questions must be considered:
8.1
Will the system be continuously deployed or event activated? It may be
deemed useful to provide continuous illumination. (This may provide a
psychological effect as well as actual.) On the other hand, depending on
the area of coverage and design objectives, the lighting system may be
event activated; that is, a specific event (detected intrusion, time
period, etc.) may trigger the lighting system to be turned on.
8.2
Will the system be target oriented or omni-directional? In some
situation, it may be desirable to illuminate an entire area of coverage.
In other settings and with different security requirements, target
oriented illumination may be sufficient, providing, in effect, pools of
light illuminating only specific objects or locations within the same
area of interest.
8.3 Will the protective lighting system be interface with CCTV or alarm systems?
What failure rates of system components or simultaneous element failures are the most critical to overall system performance?
8.4
Could the system be accidentally activated this causing an injury or
damage? This is an issue that must receive special consideration it if
is to be event activated.

9. Lighting as a Psychological Deterrent
Designers
of a protective lighting system may, in any given region (area of
coverage) and circumstance, use lighting primarily as a psychological
deterrent. Recalls that lighting as a psychological deterrent creates in
an intruder’s mind the awareness that he or she will be discovered and
observed during any unauthorized entry attempt. As a general rule,
however, designers may view psychological deterrence more as an added
benefit, given specific situations (in a design intended primarily for
object illumination or physical deterrence). When lighting is used as a
psychological deterrent, it is imperative that the lighting system be
interfaced with CCTV, alarm systems and security response forces. This
is essential in order to ensure maximum deterrent effect.

10. Security Lighting Standards
Many
turn to The U.S. Army Field Manual 19-30, Physical Security. This
manual has been used as a reference for protective or security lighting
for many years. Another resource, the Illuminating Engineers Society
(IES), Lighting Handbook, 1993, also serves as a reference for
protective and security lighting. The third source of information on
this subject is the Nuclear Regulatory Commission Physical Security
Standards. This document provides in-depth discussions on isolation
zones, protected areas, clear zones and other restricted areas requiring
protective lighting. These three resources provide essential
information. Latter on, I will discuss details of any one Security
Lighting Standards.

In my next articles, I will discuss elaborately Lighting Applications Issues.
(Part-4)
1. Introduction
In my last three discussions (Part-1), (Part-2) and (Part-3),
I have discussed Design consideration of Physical Security, Barriers,
Layers of Barriers, Type of Barriers, Perception of Protection and use
of lighting as physical and psychological deterrent. Today, I will
discuss how to design Security Lighting at workplace.
The following issues will be discussed in this article:
Application Issues
Light Intensity for Object/Area Illumination - Design Issues
Light Intensity for Physical Deterrence - Design Issues
Light Intensity for Psychological Deterrence - Design Issues
Types of Lamps
Illumination Quality
2. Application Issues
It
should be apparent from the discussions in the preceding articles that
lighting requirements vary according to each security application
(object illumination, physical deterrence, psychological deterrence).
All of these applications have different requirements for intensity,
distribution, quality, sources and reliability. In addition, appropriate
lighting for a given area is affected not just for the requirements of
the security plan for the area, but by conditions in the surrounding
areas as well.
For
example, a designer's plan for protective lighting must account for the
impact lighting from an adjacent property, especially if there is
resulting glare. In the following sections, we will focus on
illumination intensity and quality in more detail.

3. Light Intensity for Object/Area Illumination - Design Issues
With
object illumination, the goal is to provide sufficient light over the
area to detect anyone moving in or around the area. At the same time,
lighting systems should whenever possible limit the intruder's view of
the area. This strategy is intended to impair the intruder's ability to
ascertain whether they are under observation.
An effective security lighting system for object illumination should:
3.1 Discourage intruders
3.2 Make detection of attempted entry highly probable
3.3 Avoid glare that annoys neighbors, workers, security officers or passing traffic
3.4 Provide adequate illumination whether the surveillance is by electronics or the human eye
3.5 Render the observance of security posts, CCTV cameras or other electronic sensors by intruders to an imperceptible level
3.6 Provide for special treatment of entrances, exits and other sensitive locations.
Further,
such a lighting system must be designed with careful attention to
several additional factors that impact on its overall efficiency. System
designers should:
3.7 Provide reliability through redundancy of components
3.8 Provide for easy control and maintenance
3.9 Determine the required illumination by viewing the scene under varying natural light conditions
3.10
Determine the distance between the surveillance element (person,
camera) and each element of the illuminated object or scene
3.11. Determine the purpose of the observation: recognition, identification or detection.
Each
of these factors is a crucial design element which, when applied
properly to the overall lighting plan, will yield a highly effective and
efficient protection capability.

4. Light Intensity for Physical Deterrence - Design Issues
Lighting
intended to provide physical deterrence must use lighting intensity as a
method to disable an intruder. The general design principle for
physical deterrence lighting is use a level of intensity as low as
possible to accomplish the desired effect. An effective lighting system
for physical deterrence should:
4.1 Cause an inability to see normally, preventing further penetration of the area
4.2 Cause specific physiological reactions to the light such as pain or tearing and change in ocular muscle stress.
4.3
Cause temporary blinding which will vary in duration depending upon the
intensity and character of the light source. Strobing of the light
depending on its intensity and speed can cause prolonged disability to a
person. The utilization of strobing light must include a legal review
to determine what liabilities may be incurred.

5. Light Intensity for Psychological Deterrence - Design Issues
Remember
that psychological deterrence is an intruder's belief and/or perception
(perhaps accurate, perhaps not) that security at a specific location
has diminished his or her ability to overcome the security measures in
place. Lighting, as previously mentioned, can be an important tool in
creating a psychological deterrence. The objective for designers of such
a lighting system is to provide illumination intensity sufficient to
convince an intruder there is a high probability of detection,
identification or apprehension.

6. Types of Lamps
In
casual conversation, lighting terms are often used imprecisely. These
are two terms which are often used interchangeably; however, in
discussing technical lighting issues, their correct usage is important
to avoid confusion.
These are:
Lamp - the actual bulb or tube which emits light when electrical energy is applied.
Luminaries
- the lamp, housing and all other hardware used in mounting and
focusing illumination; also referred to as lighting unit, fixture, or
instrument.
There are many different types of lamps used in modern protective lighting systems:
6.1 Incandescent
6.2 Fluorescent
6.3 Mercury vapor
6.4 Metal halide
6.5 High pressure (H/P) sodium
6.6 Low pressure (L/P) sodium)
Each
has its own unique characteristics which determine when the particular
lighting is suited to a particular task. For example, low pressure
sodium provides relatively high levels of illumination at low cost.
Often they are used to light highways; however, L/P Sodium lamps tend to
distort colors significantly. Using L/P sodium lighting for a parking
lot at a car dealership, therefore, would be inadvisable, since
customers would be unable to get a true representation of the color of
the vehicle before them.
Mercury
vapor, metal halide, and high-pressure sodium are known as
high-intensity discharge (HID) lamps. These lamps provide the highest
efficiency and longest service life of any lighting type. They are
commonly used to outdoor lighting and in large indoor areas.

7. Illumination Quality
Factors to consider in selecting a lighting type are:
7.1 The lumens per watt
7.2 Color rendering
7.3 Focusing capability
7.4 Warm-up time
7.5 Re-strike time
7.6 Flicker rate
Illumination
quality is the combination of all these individual factors. As in all
security applications, determining the specific use for a system — in
this case lighting — will define the resources required — in this case
the illumination quality of the lighting system. Figure above provides
an overview of many of the factors effecting illumination quality. A
discussion of several of these factors follows.

7.1 The lumen per watt
Lumen
is a measure of illumination. Lumen per watt is a measure of
efficiency. It is the ratio of illumination to electrical energy used by
the lamp to create the illumination. Lumen (LM) per watt has
significant impact on the cost-effectiveness of the system.
7.2 Color rendering
Color
rendering is an important consideration if actual scene element colors
must be observed or color CCTV cameras are to be used to record the
scene. In such situations, it is important that natural colors not be
distorted.
7.3 Focusing capability
Focusing
is a luminaire's "spread;" that is, does it cover a wide area with
diffuse light, or can it be aimed in a narrow beam of intense light on a
small area. The intended use for a given lighting unit (object
illumination: physical deterrence, etc.) defines the type of lighting
unit required: wide or narrow focus.
7.4 Warm-up time
Warm-up
time is extremely important if maximum luminance is instantly required
at the time of activation. Compare the values in the table shown
previously.
Note
that some types of lighting require as much as eight minutes achieving
their optimum output level. In some security operations, that would
present an unacceptable risk.
7.5 Re-strike time
Re-strike
time is the period of time between a lamp's shut-down and its restart.
Some lamps can be restarted immediately; others must "rest" for as much
as 20 minutes before "re-striking." Along with warm-up time, re-strike
time is critical to systems used to protect persons or high property
value items, since such security systems cannot afford to be without
sufficient illumination for extended periods of time. Thus, the amount
of time needed to restore the system determines its value to the overall
security program. If instant re-strike is required, system designers
must include a capability for an automatic restart stand-by system.
7.6 Flicker rate
Some
lamps have as part of their characteristics varying degrees of flicker.
This may be most visible in the video produced by a CCTV camera using
certain lamps as a source of illumination. It appears as "jumps" or
rapid pulsing in the video. Flicker is a result of the alternating
current which supplies electrical power to the lamp. Some types of lamps
are more susceptible to flicker than others. In addition to affecting
video image quality, flicker rate has a more subtle effect. Individuals
exposed to flicker for long periods of time — while perhaps consciously
unaware of the phenomenon — can develop stress, and elevated levels of
stress has a negative impact on personnel both at the psycho-social
level and in terms of productivity.
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