Chapter 12
Electronic Alarm Systems
Abstract
In this chapter, readers are introduced to the five basic components in any alarm system and the three types of alarm sensors. The overall operation of an electronic alarm system, along with its potential problems and costs, are addressed. Lastly, the subject of sensors is elaborated upon to allow individuals to further grasp this aspect of security.
Keywords
Alarm circuit; Annuciator; Control unit; Sensory deviceElectronic alarm systems provide another element of defending a company’s assets from loss. An intrusion alarm system, which will detect unauthorized entries into a building, must be evaluated as to the cost of the alarm system versus the value of the items that are to be protected. For good overall security, there must be a balance between services, equipment, and alarms. A system must be planned to operate without major problems and be economically feasible for the property or building that is being protected.
Alarms can function in a variety of ways and serve a variety of needs. For example, alarms can be used to detect fire, detect an unauthorized entry, notify authorities during an emergency, monitor equipment, and report malfunctions. The need for an alarm system and the type must be evaluated according to the needs of the owners of the facility. Some facilities will be more prone to burglary or robbery while another may be more likely to be damaged as a result of fire.
There are five basic components to any alarm system: a sensory device, a control unit, an annunciator, a power source, and an alarm circuit.
A sensory device initiates the alarm signal as a result of sensing a stimulus or condition to which the system has been designed to react. Heat and smoke detectors and door contacts are examples of sensory devices.
The control unit is the final point for all sensors and switches in the alarm system. The control unit is usually housed in heavy metal, tamper-resistant cabinets. The elements within the control unit are arranged to receive signals from the sensors and to relay these signals to the appropriate final point within the control unit.
The annunciator is a visual and/or audible signaling device that indicates activation of the alarm system. A particular type of annunciator is selected depending upon circumstances and location of the alarm system and the desired or required response. For example, a bank may utilize a silent annunciator alarm to report a robbery, whereas a school would use horns, sirens, and lights to annunciate a fire.
The power source is a 110-V power system that is generally filtered to provide the proper current and voltage normally used. An emergency power source or battery backup system should also be included.
An alarm circuit is used to transmit signals from the sensors to the control unit, which in turn transmits the signals to the local or remote annunciator alarm unit. Alarm systems are either open or closed circuit systems. An open circuit uses an electrical line that does not have a flow of current present until switch or relay is closed completing the circuit. A closed circuit uses an electrical line with current flowing through it; any change in this electrical current flow will initiate an alarm.
In addition, systems can be arranged by a direct method of alarm notification or by a loop system. The loop system is referred to as the McCulloh loop (named after its inventor), which is a circuit that has two or more sensors, switches, or systems on the same circuit. The greatest advantage of the direct system is that when an alarm is received, the exact location of the alarm is known. With a loop system, only the general area of the alarm is known.
As discussed earlier, alarm sensors can take a variety of forms. Basically, there are three types of alarm sensors: perimeter or point of entry, area protection, and object protection. In a thorough security system, all three types of alarm sensors may be used in an effort to provide a high level of security.
Sensors are designed to initiate alarms under several different conditions:
1. When a surface or area being protected is penetrated.
2. When a power failure occurs.
3. When the sensors are opened, grounded, or shorted out.
4. When the sensor fails due to age or wear.
5. When the container that houses the sensor is opened.
Sensors
Electro-mechanical
Electro-mechanical sensors are considered to be reliable but may be costly. They are designed to place a current-carrying conductor between an intruder and the area to be protected. The conductor carries the current, which keeps a holding relay in an open position. If the current flow stops for any reason, the device releases the relay and allows the contacts to close so that an alarm circuit is activated.
Intrusion switches
Intrusion switches (Figure 12.1) are used on windows, doors, and skylights. The switches are made of two electrical contacts: one is installed on the opening surface (door or window), whereas the other is installed on the fixed surface.
When the surface (door or window) is closed, the two contacts provide a closed circuit so there is a continuity of current flow. When the surface is opened, the contacts separate and the electrical circuit is broken and the alarm is signaled. These switches are always installed on the inside or the side of the material to be protected.
Magnetic switch
Magnetic switches consist of a magnet and a switch assembly connected to an actuator. The switch is usually mounted on a fixed surface, with the magnet fastened to the opening surface. When the surface is closed, electrical current flows. When the surface is opened, the magnetic field is broken and an electrical current is activated and the alarm is signaled. Protection of Assets authors Walsh and Healy [1] state that the most efficient magnetic switch is a balanced magnetic type that will activate an alarm upon the increase, decrease, or attempted substitution of an external magnetic field.
Wire and screen detectors
Wire and screen detectors are used to enhance security for windows and can provide a valuable service to the home security system owner. Wire is woven into the window screen. If the screen is cut as well as the alarm wire, an alarm will be activated because the electrical current flowing through the wire has been interrupted. Screen detectors provide a good level of security, but they are not inexpensive.
Soundwave and microwave sensors
Soundwaves and microwave sensors are based on the “Doppler” principle, according to authors Walsh and Healy. Doppler was an Australian scientist who discovered that “microwaves or soundwaves are disturbed by movement” [1].
Sensors that use this principle have a transmitter that sends a wave pattern and then receives it. As long as the pattern being received is the same as the one being transmitted, a stable condition exists. A distortion of a wave pattern caused by movement is detected, thereby initiating an alarm. Soundwave or ultrasonic employ soundwaves of a higher frequency than the human ear can hear. Sensors of this type are usable only inside a building. Audio noise does not affect sensors nor does air currents. However, if heating/air conditioning air currents move displays suspended from a ceiling, the display movement may activate an alarm. Radar detectors work in the same manner as ultrasonic, but the radar wave is different. Radar can be used outside. Radar waves do not permeate construction such as plaster walls.
Capacitance sensors
Capacitance sensors are large electronic sensors that radiate energy and detect change in the capacitive coupling between an antenna and ground. These are normally low in cost and are suitable for outside use.
Vibration sensors
Vibration sensors use a sensitive contact microphone that is installed indoors on the surface to be protected. Vibrations caused by someone attempting to penetrate the surface are picked up and transmitted to an amplifier, which initiates an alarm. These are not considered useful outside.
Audio or acoustic sensors
Audio sensors are microphones that are activated when sound initiates the alarm. Audio sensors are sometimes used for vaults.
Light sensors
Light sensors operate on the principle that an alarm will be set off if there is a change of light or a beam of light is interrupted. The use of a photoelectric cell is the simplest means of changing the transmitted light beam through a propeller-like baffle. The receiver must be tuned to a frequency that matches the revolutions per minute of the monitor and vibrations in speed caused by temperature change.
Receipt of alarms
Alarms can be received at a number of different locations. Local alarm systems sound a generating device on the outside of the building to call attention to the alarm. Advantages of using a local alarm system include the following:
1. Psychological deterrent (the intruder knows that he or she has been detected).
2. Damage should be minimized because the intruder hears the alarm.
3. The alarm is inexpensive to install and easy to maintain.
Many sprinkler systems have a local annunciating system, which consists of a bell that rings as water flows through the sprinkler riser.
There are some disadvantages in using only a local alarm system, including the following:
1. Easy to defeat because of its simplicity.
2. The intruder will probably not be apprehended.
3. The alarm may be disregarded if no one is nearby to hear the alarm.
A second type of alarm system is the central station. With the central station alarm system, the alarm is not heard by the intruder; thus, it is called a “silent” alarm. Police are normally notified immediately of the alarm, which aids in apprehension because the intruder is not aware of the alarm. Many alarm companies provide a monitoring service for the central station systems. This will require the company who desires the coverage to test the system on a regular basis to ensure effectiveness. This type of system uses telephone lines to carry the alarms. Direct lines or use of a loop system may be employed to provide the service.
A third type of alarm answering system is the direct police or fire department termination. The advantage of this type of system is obvious: a quick response should be given to the alarm. However, in many cities, the police and/or fire department are not permitted to receive the alarms directly unless the facility is a school, church, or other public building.
The final type of alarm receipt system is proprietary termination. With this type of system, a facility monitors its own alarms by using either security officers, maintenance, or other employees to respond to alarms. Advantages of the proprietary system include the following:
1. System can be designed to meet the needs of the owner.
2. The system is operated and controlled by the owner.
3. Functions can be virtually unlimited if designed properly.
4. Line security is enhanced because the alarm line begins and ends on the owner’s property.
5. system can be cost-effective if designed properly.
Disadvantages of the proprietary system include the costs of providing personnel to monitor the alarms and additional costs if the system has not been designed properly. Even by using a proprietary system, security guard patrols will often still be needed.
False alarm problem
If most police officers were asked what they believe is the single greatest problem with alarm systems, they would probably answer without hesitation that false alarms are the greatest problem. Between 90% and 98% of all alarms are false. False alarms are a result of user error or negligence, poor installation or servicing, or faulty equipment.
More than 50% of all false alarms are due to user error or negligence. Because of poor insulation and service, many state and local governments have developed standards for installing and servicing alarm systems. False alarms affect police in three ways:
1. They encourage poor police searching of protected premises.
2. They cause a poor attitude toward the alarm user and alarm industry.
3. They foster a belief that intrusion alarms are more trouble than they are worth.
Solutions to the false alarm problem include the following:
1. Sell the system correctly: consider the environment, habits, and routines of subscribers, and do not overprotect.
2. Do not use space protection excessively.
3. Instruct the subscriber on the proper use of the system.
4. Reinstruct the subscriber at frequent intervals.
5. Train and retrain alarm company employees on procedures and troubleshooting techniques.
6. Maintain the system in proper working order.
Access control systems
“A Modern Tool for the Security Officer”
Access control can mean many things to many people, but for purposes of this discussion, we will define access control as an electronic means of controlling access and identifying users.
Basic access control systems employ the use of a card (typically the one- or two-door variety). They simply identify a card as valid or invalid, and on that basis, allow or deny access. The system does not identify the valid card to a particular user, and there is no hard copy report or other record of entry. In short, it is no more than an electronic key. The system does not identify who has what card, or even what card is used. If a card is coded for that door, then the system allows access. If it is not, then access is denied.
The more sophisticated systems have the ability to identify a particular card to an assigned user of the card. When the card is presented to the card reader, the system not only permits or denies access based on the validity of the card, but it also can identify the user by name, employee identification number, and access level. Beyond that, the system can also permit or restrict access by time, date, day of week, and as many as 50 access authorization levels, depending on the sophistication of the system.
These systems are every bit as important for what they record as for what they control. Every entry or “transaction” is recorded in the system. Larger access control systems can automatically log, display, and print out upwards of 1.5 million transactions. For an average larger system, this could be as much as 6 month’s worth of access information.
The ability to perform audit functions adds to the value of the access control system. Now you can answer these questions: Who went through what door? How often? What time of day or night? Did a person attempt access through a door they should not have? This information becomes very valuable when an incident occurs, such as a theft or accident. The audit trail that can be retrieved from the access control system may eliminate as well as identify suspects. Who was in? What time? Why did Mr. Smith attempt to enter a restricted area? As the capacity of personal computers continues to increase, the ability to store and retrieve information will continue to increase as well. Already, the access control system is being used for such automation functions as guard tours, time and attendance, telephone call accounting and pricing, doctor registries in healthcare facilities, copier control and pricing, and other automated functions that either save or generate revenue for the user organization.
Performance
What are the performance criteria that a company needs to look at in deciding whether to install an access control system to replace a key system or other means of access control?
1. Is the card valid? It must establish the identity of the card user.
2. Is the system reliable? Every time John Smith presents his card, it must validate his presence.
3. Is the system easy to use? It must not slow normal work flow or make ordinary tasks difficult.
4. Is the system secure? It must be resistant to counterfeiting or duplication of the card.
5. Is it durable? The system must be rugged and have a long life expectancy.
6. Is the system hardened to its environment? The system must be physically adequate to protect against force or manipulation.
7. Is the system easy to maintain? It should offer some internal guidelines for troubleshooting for the system.
System technology
There are many types of card access technologies in use in various facilities and applications. Some of those that you will likely encounter include the following:
Hollerith readers—Punched holes in card. When inserted in the reader, it provides a momentary contact closure to release a locked door. Sometimes seen in hotel rooms. Insert reader. Inexpensive, but easy to duplicate.
Magnetic stripe readers—Reads the characters on magnetic tape affixed to card. Most popular because so much information can be stored on tape. Insert or swipe reader. Relatively inexpensive, but easy to duplicate. There is also potential for vandalism because it is a contact device.
Proximity readers (RFID)—Each card is individually tuned and can be read when in close proximity of reader. Noncontact and virtually never wears out. Can often be used without taking out of wallet or purse. Noncontact. Expensive, can be duplicated, thick card.
Bar code readers—Inexpensive and good for low security areas. Easily duplicated, with some errors or false reads. Good for dual technology cards, but not for high security.
Wiegand readers—Imbedded wire, almost impossible to duplicate. Offers higher level of security than others. Noncontact for low vandalism. Insert or swipe; noncontact.
Biometric systems
Biometric systems are expensive systems designed for high security applications; however, as they gain acceptance, prices will move downward. Technology continues to change rapidly with the technology in this field. They currently include the following:
Retina scanners—Identifies the user’s unique retinal blood vessel pattern.
Hand geometry—Measures the user’s unique hand.
Fingerprints—Identifies the user’s unique fingerprints (Figure 12.2).
Voice verification—Identifies the user’s voice pattern within previously established parameters.
Video badging integration
The video badging system incorporates a digital video identification system with a door access control system. It positively identifies the user by displaying the cardholder’s picture on the monitor at the security guard’s desk the instant the card is passed through the reader. The value of the digital video image is that it allows the guard to see an image of the person passing through the door. Secondly, the video imaging system allows a quick and easy means of keeping, storing, and upgrading the employee photo identification file because it is stored on a digital disk rather than on hard film.
Access control devices
Doors, locks, or barriers commonly referred to as turnstiles work in conjunction with card access systems. As a card reader scans and accepts a card, a signal is transmitted to a barrier to open, unlock, or release a barrier in order for access to be granted. Most barriers or turnstiles are designed to prevent unauthorized access to an area and yet blend with the décor and aesthetics of the facility where they are installed.
Turnstiles are also used to direct and maintain crowd control at sports stadiums and arenas, amusement parks, and offices and factories. Special attention must be given to the type and style of turnstile that would be accepted at a facility.
User-friendliness
The modern card access systems have become quite user friendly, with one and two keystroke commands for the security guard. The manufacturers have learned over the years that not everyone is computer literate and have built their systems on that basis. Most new systems come with easy-to-understand user prompts and menu screens. The systems also provide basic troubleshooting commands to help identify problems and conditions that are not normal. Many can even tell you what to do if certain conditions exist.
Perhaps the simplest, but most important, feature of these modern systems is that they can tell you immediately who went through what door, as well as which door is propped open or ajar.
Summary
• An electronic alarm system must be planned to operate without major problems and be economically feasible for the property or building that is to be protected. Alarms can be used to detect fires, unauthorized entries, and/or monitor equipment and report malfunctions.
• The five basic components to any alarm system are:
• A sensory device
• A control unit
• An annunciator
• A power source
• An alarm circuit
• Sensors are designed to initiate alarms when a surface or area being protected is penetrated; when a power failure occurs; when the sensor is opened, grounded, or shorted out; when the sensor fails due to age or wear; or when the container that houses the sensor is opened. Sensors can be of many different types, including foil, intrusion switches, magnetic, electro-mechanical, wire/screen, soundwave, capacitance, vibration, audio, and light.
• Alarms can be received at a number of different locations, such as local, central station, and proprietary.
• False alarms are the greatest problem with electronic alarm systems. Between 90% and 98% of all alarms are false. More than 50% of all false alarms are due to user error or negligence.
• Alarms and alarm systems are like locks, fences, and other barriers in that they can provide a reasonable level of security only if used according to specifications and in conjunction with other security devices. Proper training and indoctrination of all security personnel with the alarm system is critical if the system is to work as intended.
• As a security officer, it is not necessary for you to understand the internal working of a computer-driven access control system to take advantage of its conveniences. However, it is important to note the basic instructions. Once you have that understanding, you can master the system at your own pace. It is also important to understand that the modern access control system is nothing more than another tool to assist you in protecting the facility to which you are assigned. The sooner you give in to this notion, the sooner you will be able to use it to its maximum capability.
Exercises
1. Name the three basic types of alarm systems.
2. What are false alarms usually the result of?
3. What are the advantages of a local alarm system?
4. What is primary purpose of a card access system?
..................Content has been hidden....................
You can't read the all page of ebook, please click here login for view all page.