Access Control refers to the idea of preventing unauthorized persons entrance to a property, building or room. Access control systems have become a staple in secure environments. They allow the extra security without having the potential unreliability of a person sitting on guard. By eliminating the weak link “Human Error" these systems are able to make it nearly impossible to penetrate. Physical access control systems can range from a bouncer or guard stationed at the door, or through mechanical measures such as locks or keys. With the advancements in technology there is now a need for a higher means of access control and that is where key cards and electrical access control systems come into play. Physical access control systems depend on a matter of who, where, and when system. A true access control system is used to determine “who” is allowed to enter or exit, “where” said person is allowed to enter or exit, as well as controlling “when” they will be able to enter or exit. Before technological advancements this was accomplished in part with Keys and locks, when a door was locked only those with the appropriate key were able to use the door. The problem with mechanical Key and Lock systems is that they do not restrict the key holder from entering or leaving at specific times or dates. Historically, this was partially accomplished through the usage of keys and locks. When a door is locked, only someone with a key can enter through the door, depending on how the lock is configured. Mechanical locks and keys do not allow restriction of the key-holder to specific times or dates. Mechanical locks and keys as well do not provide any sort of record keeping of key usage. Another problem with keys is that they can easily be copied or transferred to an unauthorized person. When a mechanical key is lost or the key holder is no longer authorized to use the protected area, the locks must then be re-keyed to prevent from unauthorized access. Therefore causing an extremely costly problem for any company small or large. One of the major benefits of an Electronic access system is the ability to easily delete the access of one card. No longer does a whole floor or multiple floors need to be re-keyed. Now all that needs to be done is simply delete
Mechanical Lock and Key
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that user’s key card from the main system and the locks will no longer accept that access cards credentials. Electronic access control uses computers to solve the limitations of the now dated mechanical lock and key method. A vast range of credentials can be used to replace mechanical keys. The electronic access control systems grant access based on a credential system. The credential system is like a sort of virtual key. When access is granted, the door is unlocked for a predetermined amount of time and the action is then recorded by the system. When access is refused, the door remains locked and the attempted access is recorded. The system will also monitor the door and alarm if the door is forced open or held open too long after being unlocked. There are multiple types of electronic access systems. The most common access card systems use what is called a Proximity Card. This Proximity card works by using a miniature LC Circuit. The LC circuit is a resonant circuit in which that it consists of two electronic components connected to one another, an Inductor (L) and a Capacitor (C) This circuit acts as an electrical resonator. LC circuits are used either for generating or receiving a signal at a particular frequency. When the card is brought near a Proximity Reader the reader’s electronic field generator causes the coil in the card to activate. This coil in turn charges a capacitor which activates the integrated LC circuit and outputs a card number to sensor thus allowing for access or no access. There are many different types of access control readers and are classified in three main types. Basic, Semi-intelligent and Intelligent readers. Basic or Non-intelligent readers simply read the card number or pin number and then forward that information to the main control panel. These readers typically use the LC type cards as this type of reader is the most common used. The Semi-Intelligent readers have all the inputs and outputs on the reader themselves, but they do not make any of the access decisions. When a key card is presented the reader sends the information to the control panel and waits for a response. Once a response is made then the reader will apply the power to unlock or lock the door. The last and least common version of the reader is the intelligent reader.
LC Circuit
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These readers have all of the inputs and outputs to control the access similar to that of the Semi-intelligent doors but instead this reader also contains memory and processing power in order to make the access determinations independently without having to communicate with the control panel. These units are still connected to the control panel but they only request user updates from the control panel and are able to independently run without the control panel. As shown in the figure. This is the typical wiring diagram on how to configure and set up a typical access card system. Most doors will either utilize a Magnetic Door contact or an Electric Strike system to hold the door. The more secure systems may utilize both types of locks.
Pictured above is a simple break down of the wiring topography for a typical access card system.
Pin Access Module
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There are some inherent security risks with the usage of access card systems. The most common risk of breaking the access control system is simply following a legitimate user through a door, this type of security breach is referred to as Tailgating. This is an easy problem to avoid with proper security and personnel awareness. Another way to prevent the tailgating would be the utilization of a turnstile. In very high security situations most of the risk can be minimized with the usage of a security door called a mantrap. The man trap is similar to the door system that many banks now use. One person may enter the mantrap at a time and once the person has been identified as secure the second door opens allowing the person access. The second most common risk is as surprising simple as leaving the door open. This can be done by an employee blocking open a door for easy access while transferring documents or equipment from one room to another. Luckily many access door systems can be fitted with an forced open door monitoring alarm which will sound if the door is left open for longer than then predetermined set time. The spoofing of lock hardware is actually a fairly simple method to bypass a lock. A very strong magnet can be used to move the solenoid controller bolts in electronic locks causing them to be compromised. One of the benefits of Access cards is that it requires a fairly sophisticated level of attack in order for them to be compromised. Enterprise level hackers have been able to build portable readers to capture card numbers and then are able then to send that number back to the card reader allowing for the door to be by passed. Since the card numbers are sent across to the readers with no encryption. With the increasing need for secure access systems a new and improved system has begun to be implemented. Without the need for keycards or mechanical keys the Biometric system has become a popular option for large corporations. There are several forms of biometric identification used in access control systems. The most common being fingerprint and then iris and facial recognition scanners. Biometric technology has been supported for its ability to considerably improve the security level of access systems. A major benefit of this technology is that it eliminates problems such as lost, stolen or loaned ID cards as well as forgotten Personal Identification Numbers (PINs). Majority of biometric readers work similarly, the readers work by comparing the template stored in memory to the scan obtained during the identification process. If there is a high enough degree of probability that the template in
Biometric Fingerprint Scanner
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the memory is compatible with the live scan (the scan belongs to the authorized person), the ID number of that person is sent to a control panel. The control panel then checks the access permissions level of the user and determines whether access should be allowed or denied. The Biometric templates can be backed up in the memory of the readers therefor limiting the number of users that the reader can identify without the control panel. Though most sensors can hold anywhere from 20,000-50,000 templates so that really should not be a problem. User templates may also be stored in the memory of the smart card, thereby removing all limits to the number of system users (finger-only identification is not possible with this technology), or to make things simpler a centralized server PC may be utilized as the template host. These systems are classified as "server-based verification". In these systems the reader will first read the biometric data scanned and then forward the data to the main computer for analysis. Server-based systems can support a gigantic number of users but are dependent on the consistency of the central server, as well as communication lines between the Reader and Server. Most of these systems will utilize a rack-mounted server PC as displayed here to the right. A server by definition is a computerized system that receives and responds to requests across a computer or wireless network to either provide, or help to provide, a network service. Servers can be run on a dedicated computer, which is also often denoted as "the server".
Rack Mountable Server
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Servers operate within what is called a Client-server architecture. Servers are computers that run a certain set of programs that respond to the requests of client computers or devices. In the case of access control systems the server houses all of the credentials and user information for the Access Card Systems. All of the readers will be wired into a circuit board which will then In turn be connected to the Server machine. All of these aforementioned systems run off a credential based authorization. Be it a physical key or an access card or even your fingerprint. Each of these are considered to be your credential or authorized access device. The recommended wire to use for control door access is called composite access control wire. It is fairly similar to Cat5e wiring. One major difference being that access control wiring has no twists in the wire. It is always recommended to use plenum rated wiring. The Reader typically utilizes 6 conductor 22 gage shielded wire. The different locks typically use, 4 conductor 18 gage unshielded. The Contact and Request to Exit both utilize either 2 or 4 conductor 22 gage wires. Pictured to the right is a Maglock which utilizes an electro magnet to lock and secure the door. These mag locks are one of the easier locks to install as there are generally no interconnecting parts it is simply the magnetic force that keeps the door shut. The standard sized maglock can apply a 1,200lbf or foot pounds of holding force. There are two main types of mag locks these are defined as either Fail-Safe or Fail-Secure locks. A fail-secure lock will remain locked when power is lost. Whereas the fail-safe type will unlock when power is lost. There are a few advantages to utilizing a Maglock. The Maglock is fairly easy to install, they offer quick operation as they immediately unlock when the power is cut and because there are no moving parts there is nothing to break. The two disadvantages of using a maglock are that it requires a constant power source and is very expensive in comparison to other mechanical locks.
Maglock
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An Electric Strike lock is a very popular access control device used for door frames. It is exchanged with the standard fixed strike faceplate that is normally used with a latch bar type lock interface. Similar to a fixed strike, the faceplate presents a curved surface to the locking latch allowing the door to close and latch, however, with an electric strike's curved surface, it is able to be pivot the curved surface out of the way allowing the door to simply push open without the need to turning the lock or door handle. After the door has been opened past the mechanical locking section of the faceplate, the curved piece then returns to its standard position and re-locks when the power source is removed or applied. Just like a Maglock, Electric strikes are usually available in two configurations: Fail-secure. Also called fail-locked or non-fail safe. In this configuration, applying electric current to the strike will cause it to unlock. In this configuration, the strike would remain locked in a power failure, but typically the mechanical lock can still be used to open the door from the inside as opposed to the secure side. These units can be powered by alternating current, which will cause the unit to buzz, or DC power, which offers silent operation, except for a "click" while the unit is powered. Fail-safe. Also called fail-open. In this configuration, applying electric current to the strike will cause it to lock. It operates the same as a magnetic lock would. If there is a power failure, the door opens merely by being pushed or pulled. Fail-safe units are always operated with direct current. Electric strikes are sometimes equipped with buzzers that allow someone outside the door to hear when the door is open. The buzzing noise is typically made by applying alternating current (AC) to the strike instead of direct current (DC). When using a DC powered strike, a buzzer accessory can be added to create the buzzing noise, if desired.
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There are many manufacturers of strikes, and there are many things that have to be considered when buying one, i.e., type of jamb, type of locking hardware, whether one requires fail-secure or fail-safe, length of latch, depth of jamb, voltage requirements and the length of the faceplate. Before using a magnetic lock, the Fire Marshal or appropriate authority should be consulted. Another type of door sensor which can work in conjunction with a Maglock or Access Card System is the Motion Detector. An electronic motion detector holds a motion sensor that converts the detection of movement into an electronic signal. This is accomplished by measuring optical changes in the sensors field of view. Most inexpensive motion detectors can detect motion up to 15 feet or 5 5 meters away. The more expensive systems utilize multiple types of sensors at once and are able to detect from much longer ranges of distance. A motion detector can be connected to either a burglar alarm, which is used to alert the home owner or security service after it detects motion, or to an Access Control system which can be used to unlock an exit door when motion is detected. These sensors can also activate a camera system to begin recording when motion is detected so that the area in question is properly surveyed. Motion detectors have found countless applications in home and business applications.
Motion Sensor
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ASSOCIATED TECHNICAL COLLEGE
Security Systems
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Security alarms are often used in residential, commercial or industrial facilities for protection against Property damage, burglary, as well as protection against trespassers. Similarly, car alarms protect vehicles and their contents. Amazingly both vehicular and commercial alarm systems follow the same basic design concepts utilizing a controller, sensors and the alarm notification unit.
There are two main types of Alarm Systems. Closed and Open Circuit Systems. In a Closed-Circuit system, the electric current is “closed” or flowing when a door is closed. This means as long as the door isn’t opened the electricity can flow through the circuit. Once the door is opened the circuit is then opened as well causing the flow of electricity to stop, therefor triggering the alarm. In this system the circuit is installed inside of the door frame and the magnet is installed in the door.
In an Open-Circuit system the operation of the system is the opposite. A closed door keeps the circuit open with no flow of electricity. Opening of the door causes the circuit to close giving the alarm system a flow of electricity and thus triggers the alarm. In this system the magnet is installed in the door frame and the circuit is installed in the door. This adds a few more steps to the installation process as the wiring of the circuit needs to be wired all the way through the door and through a door frame in order to reach the alarm system.
The more commonly used system is that of a Closed-Circuit. The main reason being that a closed system is far more secure and much easier to install. A closed circuit system always has a constant flow of electricity going through the alarm. Should an intruder find the wires for the door sensor and cut them, the alarm system will trigger because of the opening of the circuit. The tampering of wiring has little to no effect on an Open-Circuit system. Having to drill through and across a door is never an easy task to undertake and there is always the risk of damaging the doors integrity and as such the Open-Circuit system is typically not a recommended option.
Most basic alarm systems consist of multiple sensors of varying types in order to detect intruders. A common security alarm setup utilizes these following components. Premises control unit (PCU) is the brain or CPU (Central Processing Unit) of the alarm system. The PCU is the device that reads the sensors inputs and tracks the arming and disarming of the alarm system if hooked up to a phone system this PCU can dial 911 if an intrusion is detected. Most modern systems, contain
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one or more PCU circuit boards inside of a metal enclosure located in a discrete location in order to prevent tampering.
Most systems come with at least one Touchpad. This unit should normally be placed near the most commonly used entrance/exit. This is where the alarm will be activated and deactivated. A majority of these systems utilize a pin or passcode system. Some of the newer more sophisticated systems utilize a key fob similar to that used for locking and unlocking a car.
Some Alarm systems have the option of installing a panic button. The purpose of the panic button is to alert the alarm monitoring company of an emergency situation that requires immediate response by the police. This is also classified as a Duress Alarm.
Sensors are specialized devices that are probably the most important piece of equipment in any alarm system. These sensors are the determining item for detecting intrusions. Sensors are typically placed at the perimeter of protected areas, or up in the corner of rooms to allow for full coverage. Sensors can detect intruders by a vast variety of methods, such as monitoring door and window openings via magnets or pressure sensors. As well as monitoring unoccupied rooms for motion, sound or vibrations.
There are many different types of detectors, the most common being the passive infrared detectors. A passive infrared sensor or (PIR) is utilized to detect motion. The PIR offers inexpensive and reliable functionality. The term passive denotes that the sensor does not produce its own energy; it works entirely by detecting the thermal energy given off by other objects. PIR sensors do not actually detect motion, they perceive rapid changes in temperature at a given focal point. As an intruder walks in front of the sensor, the temperature at that spot in the room will rise from room temperature to body temperature, and then back again. This quick change is what triggers the detection.
PIR sensors are designed to be wall or ceiling mounted, and come in numerous focal ranges, from narrow "precision" detectors to 360 degree wide angle view.
Passive Infrared Sensor
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One of the less common detectors is the Ultrasonic detector. This detector functions by emitting a 15KHZ to 75 KHZ (kilo hertz) frequency which is inaudible to the human ear. The Doppler shift principle is what causes this system to work so well. This principle is described as the change in frequency when an object bounces the audio back and thus the sensor detects object motion. This is caused by a moving object changing the reflection properties of the sound waves around it. Two important conditions must be met in order for this system to remain successful. First, there must be motion of an object or individual moving towards or away from the receiver. Secondly, the motion of that object must also cause a change in the Ultrasonic properties of the frequency in order for the sensor to detect a difference. This detector operates by detecting the amount of signal received. Hard surfaces like walls and floors tend to bound back a majority of the signal where as soft surfaces like human skin or clothing absorb most of the energy causing a signal loss to be detected by the sensor. When the surfaces are stationary, the frequency of the waves detected by the receiver will be equal to the transmitted frequency. However, a change in frequency will occur as a result of the Doppler principle. When a person or object is moving towards or away from the detector, it initiates an alarm signal. This technology is considered obsolete by many alarm professionals, and is not actively installed.
Another detector that utilizes the Doppler Shift principle to detect motion is the microwave detector. This device works by emitting microwaves from a transmitter and then detects any reflected microwaves or reduction in beam intensity. The transmitter and receiver are usually combined inside a single casing for indoor, and separate casings for outdoor. To reduce the amount of false alarms, this type of detector is usually combined with a passive infrared detector. Microwave detectors work by detecting a sudden drop in the level of received or reflected energy. Microwave detectors are a less popular option because of the concern that the detector may be dangerous to one’s health due to the emission of microwave radiation. Although the amount of actual radiation emitted is 0.0001 or the equivalent to the amount one would encounter while walking down the street on a normal daily stroll. Many people still refuse to use this because of the connection to the idea of this emitting the same waves as a microwave oven.
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One of the more well-known sensors is the Photo-electric beam detector. Almost everyone has seen these in popular Hollywood action movies. Photoelectric beam systems detect the existence of an intruder by transmitting visible or invisible infrared light beams across an area. Usually across a walkway where the beam can become obstructed. To improve the detection surface area, the beams are often employed in stacks of two or more. However, if an intruder is aware of the technology's presence, it can be avoided. The technology can be an effective long-range detection system, if installed in stacks of three or more where the transmitters and receivers are staggered to create a fence-like barrier. Systems are available for both internal and external applications. To prevent a clandestine attack using a secondary light source being used to hold the detector in a 'sealed' condition whilst an intruder passes through, most systems use and detect a modulated light source. The picture above shows what a visible photo-electric barrier can look like when set up in a dark room.
Another popular sensor is the glass break detection sensor. This can be used for interior perimeter protection, more specifically the windows. Glass break sensors work by acoustically detecting the sound frequency associated with breaking glass. This is typically done with a small microphone located inside the sensor which listens for specific frequencies. The more sophisticated systems will house a small memory chip inside which has recordings of glass breaking. When the sensor
Photo-Electric Beam
Glass Break Sensor
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detects any sounds it compares it to the database of sounds, if there is a match or a sound similarity reaches a certain threshold the alarm is then set off. Another type of glass break sensor is the Seismic glass break detector which is a shock sensor which is installed on the pane of glass. When the glass is broken it sends a specific shockwave that travels across the glass and hits the sensor causing it to trip the alarm. This frequency is typically in the 3 to 5 kilohertz range. The sensor pictured above is a Shockwave sensor.
These next sensors can be used as standalone or independent systems or can be tied into an existing alarm system. Carbon Monoxide, smoke and heat detectors are the usually all included in one housing that will contain the three sensors in one. These are typically 24 hour zones meaning they are always on. The smoke and heat detectors are used to protect from the risk of fire, where as carbon monoxide detectors protect from the risk of the Carbon Monoxide poisoning. Traditional smoke detectors are mini ionization sensors which create an electric current between two small metal probes. When smoke enters the detector it causes the electric current to be stopped causing the alarm to sound. The ionization alarm is able to quickly detect even small amounts of smoke produced by even the smallest of fires. Another type of smoke detector is the photoelectric sensor. It works on the same premise as the photo electric sensor discussed earlier. This sensor contains a small light source as well as a light sensitive sensor. The light in this sensor is designed to miss the sensor at all times. When smoke enters the sensor the light beams reflect off of the smoke and then reflect onto the light sensitive sensor causing the smoke alarm to sound.
A Magnetic Reed Switch is an electro mechanical device that activates an alarm when its magnetic connection is broken. These are commonly used on doors. Because the glass in a window can be easily broken to avoid setting off a magnetic sensor, which is why windows usually have either a glass break sensor either near or on the window. The magnetic sensor is installed in the door frame and on the door. It contains two magnetic bars that when the door is closed are either touching or very close to one another. When a door is opened with the alarm still on the connection between
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the magnets disappears causing the circuit to break, therefor setting off the alarm. This works when the door is closed the magnet on the door pulling the switch in the circuit closed allowing the flow of electricity. When the door moves away the circuit snaps back open and cuts off the electricity. This works when the door is closed the magnet on the door pulling the switch in the circuit closes, allowing the flow of electricity. When the door moves away, the circuit snaps back open and cuts off the electricity.
Installing the sensors and control unit is the first and one of the most important steps in setting up an alarm system. One of the final steps that is equally as important would be the devices which are utilized to sound the alarm. There are many different ways that an alarm system can handle the detection of an intruder. In more advanced systems the main control center will be wired up to more than one alerting device. Typically, when the alarm is triggered an alarm system will send a trigger signal to a siren or buzzer or any other sort of loudspeaker type of device. Many will also have strobe lights or flashing amber lights to signify an alarm. Most systems also contain what is called an Auto-Dialer, which is a system that automatically dials either the alarm company’s headquarters or depending on the alarm triggered dials 911 automatically.
The sirens and lights serve a few main functions. First these alerts are utilized to alert occupants and neighbors that someone has broken into the house or business. Secondly, once the intruder realizes that there is an alarm he or she will be far less likely to stay around for a long period of time. Lastly the benefit of bright flashing lights and a loud siren is that it makes it far less complicated for the police to identify which residence was broken into.
Large Alarm Sirens
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The telephone auto-dialer can serve a couple functions of its own as well to aid in the speedy response of an alarm being triggered. One of the beneficial functions of the Auto-dialer is the ability to dial the police directly, and play a pre-recorded message which gives the address of the house or business as well as any other relevant information. The message usually repeats itself so that even if the call is put on hold it will continue to play for some time. The auto dialer as well can simultaneously dial the company that manages or installed the equipment and relay important information about the intrusion and allow the company to then relay that information to the police.
When household and business alarms were first installed, they were heavily reliant on the phone line for communicating with the monitoring company or police station in the case of an intrusion. In order to prevent any alarm from dialing the police as seen in many Hollywood movies. The perpetrators would simply identify the phone line that the alarm was using and would either route it to another phone or simple cut the line. This worked well for a while until alarm companies found a way around it. The alarm companies discovered that if they kept a live connection between the alarm system and their servers they could monitor when a phone line was cut. This made it impossible to trick those systems by tampering with the phone line. Anytime there is an outage in signal from the phone line, the alarm company will immediately notify the customer via cellphone or a secondary line, if no response is received the police are then dispatched. To counteract this problem of relying on a hardline for communication, many of the newer alarm systems offer the option of a Cellular Auto-Dialer. The cellular dialer is a much safer alternative. With no hard ties to the outside even when power and or the phone line is cut the alarm system is still able to dial out to the police or the alarm company.
The next decision any person or company having an alarm installed is whether they want the system to be a Monitored or Unmonitored system. The Monitored system being one where a private organization monitors or watches the system 24 hours a day 7 days a week and will alert the police if something goes wrong and the owner cannot be contacted. The benefit of these systems is once the alarm is triggered the house phone is rang and the operator asks a couple questions regarding who is the person who answered the phone and what the alarm code is or asks them to answer a security question. Unmonitored systems have on-location flashing lights and sirens but usually do not have auto-dialer systems.
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The benefit of having a monitored system over an unmonitored can tie into the control of the Auto-Dialer. In most cases with a monitored system before the call goes to the police the alarm company is notified first. As such they are able to determine whether this was a false alarm or whether the alarm was sounded for a legitimate reason. With an unmonitored system each time the alarm is triggered the police are automatically notified, and as such if false alarms happen the owner of the alarm system can be fined quiet heavily for the unnecessary police call. False alarms are a big concern for the police. These false calls take up a significant amount of police resources and end up taking police away from their main business of preventing and detecting crime. The first time a false alarm occurs the police will issue a warning, if it happens more than a second time large fines can and will usually be assessed.
There are a few things that can cause false alarms. The most common being a power failure or power surges. This is why it is always important to make sure that the alarm system is properly grounded and powered through a backup battery. The backup battery will ensure that the system has a constant and stable source of power that will not be affected by surges.
Another problem can be attributed to improper installation. The alarm systems weakest link is bad installation. If the wires are loose or are able to be tampered with easily and not properly hidden, can cause the system to be unstable and or unsecure. Proper maintenance as well plays a huge role in the reliability and longevity of any alarm system. Making sure that the sensors are kept clean and properly aligned helps to maintain the stability of the system.
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ASSOCIATED TECHNICAL COLLEGE
Satellite Systems
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Satellite Communication Systems have come a long way since there original conception. Satellites are now an important part of our everyday lives controlling everything from cellphone reception, GPS and Television broadcasting just to name a few. A satellite is an artificial object which has been placed into orbit. These objects are called artificial satellites to distinguish them from the natural satellites currently orbiting the earth. Our Moon is a natural satellite. Satellite Dish’s are used to communicate with the orbiting satellites.
The dish is utilized to receive microwave signals from the communications satellites orbiting in space. Satellite dishes are a concave shaped type of parabolic antenna. This antenna is given this name due to the parabolic reflector that gathers and focuses the signal. This curved surface has the geometric shape of a Parabola. The reflector can be made out of many different materials, the most common being sheet metal. The most important aspect of any dish is the shape and angle of the dish. This needs to be accurate to within a fraction of a wavelength or degree. This is why the parabolic design is the most popular as it enables the highest signal gain and best focal qualities for a satellite dish. The shape of the dish is designed so that the microwave signals are reflected to the dish’s focal point. The focal point is where the Low Noise Block down-converter or LNB is located. The LNB converts the signals to electrical signals and shifts the signals from the downlinked C-band or Ku-band to the L-band range.
There are many types of satellite dishes and most of these parabolic antennas are distinguished by their unique shapes and focal location types. In parabolic or dish antennas the reflector is shaped like a parabola in a circular rim. This is the most common type as it best reflects the signal into a narrow pencil-shaped beam along the center of the dish. Displayed to the right are the four main styles of parabolic satellite dish’s. The kind used with most satellite companies is typically the Axial or Front Feed which allows for multiple points of signal reflection and gives the highest gain with a more relaxed approach to precision of aiming.
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Pictured to the left is an Axial or commonly known as a front feed satellite dish. This is the most common type of feed for satellites, with the feed antenna located in front of the dish at the focus point. One disadvantage to this type of dish is that the feed is in the way of its own incoming signal and as such can only maintain a 55-60% efficiency rating.
Displayed on the right is an example of an off-axis or offset feed satellite dish. This dish has an asymmetrical parabolic reflector. This means that the focus point and the actual feed of the antenna are located to one side of the dish. The reason for using this design is to keep the feed antenna out of the way of the signal path. Therefor allowing this dish to not block the beam. It is widely used in home satellite television dishes, which are small enough that the feed structure would otherwise block a significant percentage of the signal. Offset feed can also be utilized in multiple reflector type satellite dish’s as seen below with the Cassegrain and Gregorian.
Axial Satellite Dish
Offset Feed Dish
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Pictured to the left is a Cassegrain satellite dish. This dish works by reflecting the signal off of the larger dish towards a smaller convex secondary reflector and back down in a concentrated beam towards the feed LNB which is located dead center of the dish. The signal waves sent from the feed reflect back off the secondary reflector to the dish, which forms the outgoing beam. Overall efficiency is around of 65–70%
Another common variation of the parabolic antenna is the Gregorian. This dish reflects signal to a secondary concave reflector which then refocuses the beam to the center of the original dish. Both the Cassegrain and Gregorian offer a stronger signal efficiency due to the secondary dish refocusing the beam. Similar to the Cassegrain design except that the secondary reflector is concave. Which allows the overall efficiency to increase to over 70% or even higher depending on the placement of the dish.
Cassegrain Dish
Gregorian Dish
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Another common type of dish is called a shrouded dish. This is a dish with a circular metal shield attached to the rim of the dish. The shroud shields the antenna of radiation from angles outside of the main information beam. The shroud is able to reduce the signal interference by at least 10dB. It is used to prevent interference in microwave links, which is most prominent where there are several antenna feeds utilizing the same frequency and are located in close proximity to one another.
Similar to the shrouded dish is the cylindrical dish. The reflector for a cylindrical dish is curved in only one direction and flat in the other. The radio waves come to a focus not at a single point but focus along a line. The feed is sometimes an antenna located along the focal line. This picture shows Shrouded and Cylindrical dish’s next to one another.
The idea of using parabolic reflectors for radio antennas was originally taken from optical technology. This was discovered due the power of a parabolic mirror and its ability to refocus light into a single highly focused beam. The designs of some specific types of parabolic antenna, such as the Cassegrain and Gregorian, come from similarly named types of reflecting telescopes, which were invented by astronomers during the 15th century.
Communications satellites or Comsat as the industry refers to them, is an artificial satellite that orbits in space providing wireless telecommunications. Modern communications satellites use a variety of orbit paths, Geosynchronous and elliptical orbits. For a fixed point to point service the satellites are geosynchronous, this is mostly utilized by line of sight type communication which is commonly used for GPS (Geosynchronous Positioning Satellite) and for Television and Radio Broadcasting as well as long distance phone communications. From an observers point of view on
Shrouded and Cylindrical Dish’s
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earth a satellite in a geostationary orbit would appear that it is motionless remaining in a fixed spot in the sky. This is because this satellite revolves around the earth at the same velocity that the earth rotates which is 360 degrees every 24 hours this is called an equatorial orbit. A geostationary orbit is most useful for communication satellites because the ground antenna can be aimed at one spot and will not need to constantly be repositioned to track the satellites motion. In applications like cellular networks and Television broadcasting where a vast number of ground antennas (satellite Dish) are used this makes the cost and complexity of systems much lower and simpler. Without the need for motorized antennas the cost of the satellite dish lowers significantly.
The concept of geostationary communication satellites was first thought of by Arthur C Clarke. In October of 1945 Clarke published an article called “Extra-terrestrial Relays” in which he described the fundamentals needed for deployment of geostationary artificial satellites. Because of his discovery the area in which artificial satellites can remain geosynchronous in orbit is called the Clarke Belt. The Clarke belt is a circular orbit that is 22,236 miles above the earth’s equator. This orbit is also 165,000 miles long. In order to maintain this orbit a satellite must travel at roughly 7,000 miles per hour. Due to the Orbital Velocity that is achieved at 7,000 mph the satellite is travelling at a near constant falling and drifting away speed. Without gravity the satellite would continually drift further and further into space but at this exact speed the satellite is able to maintain its orbit without drifting away or without falling down and crashing into earth.
Another common type is the Low earth orbiting satellites. A low Earth orbit commonly referred to as LEO, is a circular orbit about 120 miles above the earth's surface and takes about 90 minutes to revolve around the earth. Because of the lower altitude, these LEO satellites are only viewable from within a small radius of roughly 600 miles below the satellite. The orbital velocity of these satellites is a little over 17,000 miles per hour any slower and these LEO satellites would fall back
Orbiting Satellite
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down to earth. Due to the satellite moving faster relative to earth’s rotation, there needs to be a large number of these satellites in the sky in order to maintain uninterrupted service. One major benefit of the Low-Earth-orbiting or LEO satellites is that they are far less expensive to launch into orbit than the geosynchronous or Clarke Belt satellites. Due to their proximity to the ground they do not require as high of a signal strength.
Fixed Service Satellites or FSS as they are referred to in the industry use the C band signal type, as well as the lower portions of the Ku bands. These are normally used for broadcast feeds to and from television networks and the other local affiliate stations.
Free-to-air satellite TV channels are also usually broadcasted on FSS satellites in the Ku band. The three major free to air satellites that broadcast over North America are the Intelsat Americas 5 the Galaxy 10R and the AMC 3 satellites. These satellites utilize the Ku band transponders for signal reception.
Satellites come in all shapes and sizes and serve a vast variety of purposes. Weather satellites are utilized to help meteorologists predict the weather and have a bird’s eye view of the weather systems developing. These satellites usually have large cameras that can send snapshots of earths weather to weather stations. As we have discussed in this text there are a vast number of Communications satellites as well including broadcast satellites which are utilized for TV and Radio Broadcasting. These satellites are used for telephone or data conversation handling. The most important feature of any communications satellite is its signal transponder. The transponder is a receiver that receives a radio or microwave signal and then amplifies it and relays it to another satellite or down to earth. A typical communications satellite can contain hundreds or thousands of different transponders. These communications satellites are almost always geosynchronous.
Because the Free-to-air systems operate at a much lower frequency and power level than other types of satellites these dish’s need to be significantly larger than those used by Dish or Direct TV. FSS satellites require a much larger dish for reception (3 to 8 feet (1 to 2.5m) in diameter for Ku band, and 12 feet (3.6m) or larger for C band).
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Another common use of satellites is The Global Positioning System or commonly referred to as GPS, is an orbit based satellite navigation system that provides accurate location and date and time information in all weather conditions almost anywhere on or near the Earth where there can be an unobstructed line of sight to four or more of the GPS satellites. This system provides critical navigational capabilities to military, commercial and public users around the world. It was started and is maintained by the United States government and is a freely accessible tool for anyone with a GPS receiver. Pictured above is the GPS-III satellite.
The GPS project was developed in early 1973 to overcome the limitations of previous navigational systems. GPS was created and realized by the U.S. Department of Defense and was originally run with 24 satellites. It became a fully operational system in early 1995.
In addition to GPS, other systems are in use or under development. The Russian Global Navigation Satellite System (GLONASS) was developed simultaneously with the United States GPS, but due to it not having a complete coverage of the globe this system was not utilized until nearly 2005-2006 when the GLONASS system was brought on par to the GPS standard.
GPS Satellite
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Pictured to the left is an illustration of the GPS constellation. This is an accurate representation of the orbits of the satellites orbiting the earth involved in GPS. The space segment currently contains about 30 operational GPS satellites orbiting the earth. Of the 30 24 are required to be functioning at all times to ensure proper function of the GPS. They orbit at a height of almost 13 thousand miles above the earth's surface. Each of these satellites will complete a full earth orbit in about 12 hours.
Building such complex machines requires lots of planning and resources, which is why, historically, only government agencies and only the top fortune 500 corporations have been able to get into the satellite or satellite launching business. Majority of the cost of a Satellite is in the advanced equipment inside of the satellite these can include Advanced computer systems and high resolution cameras that are able to read a vast array of light from ifrared to gamma and more as well as the many communication transponders. A typical weather satellite costs roughly $290 million to make. Another important factor with these satellites is the cost to launch them into orbit. Launching a single satellite into space can cost anywhere between $10 million $400 million dollars depending on the rocket used and the weight and size of the satellite.ll monetary figures are in 2000 U.S. dollars.)
GPS Constellation
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ASSOCIATED TECHNICAL COLLEGE
Surveillance Systems
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Surveillance systems come in a variety of shapes and sizes, they can be used for many different purposes. Camera Systems can be used in conjunction with access card control systems like those you find at the front door to a luxury apartment complex or more advanced security systems more commonly found in downtown business high-rise buildings. Security Camera systems are the most common and can be one of the more affordable choices when compared to other security systems. Security cameras can be found in two types, Wired or Wireless. Which setup best suited for a job all depends on what type of installation and what kind of location the cameras will need to be in. One idea to consider on what type of camera to use depends on how visible the cameras need to be. Wired cameras are a little more difficult to install. By having to run wires and hide them properly makes this a safer yet more difficult alternative. Typically with a wired system there is a higher image quality than that of wireless systems. Since the signal is travelling via wire there is little to no interference in image quality. Wireless cameras are far more flexible and easier to install. Most Wireless camera systems operate on the same platform as many other wireless devices, such as Wi-Fi routers, cordless phones and baby monitors. Most wireless technology uses a 2.4 GHz or 5 GHz Radio Signal to communicate. Because of this common wireless communication method it is quite common for these systems to interfere with one another and as such may interrupt the camera’s video broadcast signal. Also, keep in mind that if you decide on a wireless system, there's a possibility your video feeds could be intercepted by others. One of the main reasons for getting a camera system is for home or business security. With wireless camera systems you are not always sure if the wireless signal is encrypted and how well encrypted the signal may be. Having a system that may be easy to monitor by another party without your knowledge defeats the purpose of having a security system. Before any wireless install check with the manufacturer to see whether the wireless signal is encrypted or not. A Wireless camera uses what is called a NVR of Network Video Recorder. The NVR is a program that can store video from the network cameras and will allow for the viewing of multiple cameras at once.
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Wireless security cameras typically are the most popular choice with homeowners. The wireless camera systems are quite small and can be far less complicated to set up. Most wireless systems are plug and play and require little to no technical knowledge in order to set them up. One benefit of the wireless camera is that these cameras can typically be installed just about anywhere in range of the wireless receiver. The only thing that needs to be planned is getting power to the camera and once that power is initiated the camera will begin to transmit data to the NVR.
The Low-end to mid-range wireless security cameras are fairly inexpensive. Although being quick and easy to install is a huge advantage of the wireless systems, there are a few disadvantages as well. One downside is that even though these are wireless camera’s they still need access to power. Having to use a power cable means that though this is a wireless transmitter it is still in essence a wired camera. One way to circumvent this problem is to purchase an adapter that allows the connection of a battery or solar panel to the camera. Another disadvantage of this system is the high risk of signal loss and interference. Interference can be caused by many devices rather easily, for instance cellphones, cordless phones and thick walls just to name a few. This can cause the feed to skip or become unclear or disappear altogether. Though newer models are able to create a stronger signal there is always this increased risk involved when using wireless over wired systems. After you've determined the location or locations that will need surveillance, it is always important to have everything planned out and prepped beforehand. Most camera systems are fairly simple to install. With the advancement of Camera System technology most are up and ready to go with little to no programming out of the box. The most complicated part of setting up a Camera System is the wiring and installation stage. The location of the camera and the type of camera for the location is very important. Each camera has its own viewing angles and some are better suited for certain locations over others. It is always good to determine which type of camera should go where.
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TYPES OF CAMERA’S
Wired camera’s come in many sizes and resolutions. The Larger cameras are typically installed in areas where a business wants people to know they are under video surveillance. For instance the photo to the right shows a Bullet Camera installed onto a light pole at a public intersection. The smaller cameras are found in typically either a Dome or Bullet fashion. Most bullet cameras have an IR (Infrared) function built in which allows them to see well at night. Infrared Bullet cameras have the ability to see at night. In many cases like the camera pictured above you can see a glowing red or purple light emitting from the camera a night. This infrared allows the cameras to see dark rooms almost as well as a fully lit room. IR security cameras work off of reflected infrared light. Bullet cameras depend on a high amount of IR light in order to work correctly. Night-time imaging is typically black-and-white or monochromatic. During daylight and when adequate light is available, the camera will produce a standard color image. When the amount of ambient light drops to a factory preset level the camera will automatically switch from standard to infrared mode. When an IR camera switches to its IR/night mode the IR LEDs (Light Emitting Diode) become active, the Video output becomes black-and-white. The image quality and distance that is able to be seen by the camera all depend
Bullet Camera
Bullet Camera with Infrared activated
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on the amount of IR light emitted and received by the camera lens. IR LEDs come in multiple sizes though most tend to be quite small as manufacturers try to squeeze in as many as possible into as small an area as possible. Although IR LEDs help to make night vision possible they have some problems as well. The biggest issue is glare. Glare occurs when the IR light emitted from the LED either strikes the inside of protective glass and reflects back into the lens causing a fog like haze or reflections off of shiny gloss like materials in the focal area. This can make images appear washed out or can cause unwanted light and dark spots. While the IR light itself cannot be seen with the naked eye, most digital cameras and cellphones are able to detect it. In many cameras the LEDS glow. Majority of IR surveillance cameras use an 850nm (Nanometer) IR light. Most people want to have the cameras in place as a deterrent to crime, so it only makes sense that if you can see the IR cameras at night them too and likely seek an easier target.
Dome Cameras are used for either indoor or outdoor use and are perfect for areas that require a narrow field of focus. For instance doorways, hallways and other long distance areas that have a narrow viewing area. Dome Cameras are one of the more popular choices due to the ability of the camera to be discrete about the location being recorded. Because of the nature of the dome and the small viewing angle it can make it difficult for the people being surveyed to know exactly where the camera is watching. Dome cameras offer the most discrete surveillance options. The most secure of the dome cameras are the ones with black colored housing, as this makes it far more difficult to analyze the location of surveillance.
The acronym TVL stands for Tele-vision Lines of resolution. These are the vertical lines that make up the picture displayed on your monitor. Resolution can be one of the most confusing aspects when choosing the correct camera. The term television lines can be described as the maximum number of light and dark lines that alternate so that there is a resolved image height. If you were to break down a 480 TVL resolution you would have 240 distinct dark lines and 240 distinct white lines of resolution. Television lines is the method in which you will determine the quality of the camera or monitor will be able to display, and should not be confused with
TVL Diagram
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the horizontal scanning lines of a typical television broadcast. Standard NTSC (National Television System Committee) which is the standard used here in the United States, uses only 525 lines of image information and as such is much more limiting than that of PAL Phase Alternating Line or European standards of 625.
If you look at a television in terms of analog resolution, there are not a defined number of pixels. The discernable amount of horizontal and vertical lines that are on the screen is referred to as television lines. An analog security camera is going to be measured in analog television lines with most of them being between 420 and 580, but there are a couple of brands that make claims that their products can produce 630 or more television lines. You are going to capture a higher amount of information, if you have a higher number of television lines. This will also give you higher resolution and a greater amount of detail within the picture. You can connect this particular type of camera to a security Digital Video Recorder or CCTV VCR through the use of a video cable. Once everything is connected, you will be able to record the signal and view it a later time or you could transfer it over the Internet.
The smallest element in a digital image is the pixel. Everyone at some point in time has probably zoomed to close to and image on a website and watched it go from being clear to becoming a bunch of multi-colored little squares. Each one of those little squares is referred to as a pixel. You can have different types of resolutions within graphics and images, just like with a camera or monitor. Artists have been known to create and produce work that is at a higher resolution than what monitors are able to handle, which allows you to be able to zoom in on the image without having to worry about distortion. Most of the common computer monitors are 1024 x 768 or 1280 x 1024 pixels. A digital camera generally has a resolution of between five and eight megapixels. The majority of security cameras are going to give you a resolution of between two and three megapixels. A megapixel is the equivalent of one million pixels. It is the specific measurement for the amount of digital resolution that is encompassing the area of the output video, or the height by the width. Before any type of installation is attempted there are a few things that need to be considered. In most states, when there is recording taking place, either audio or video, there needs to be an alert or sign that notifies anyone that they are under surveillance. For instance, if you record someone's telephone conversation without them knowing it, is illegal. It's also true that if
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you install a tiny camera into a room in your house without letting anyone know it's there, you're technically breaking the law. If anyone found the camera and wasn't previously aware of its existence, you could potentially face charges. So it is always a good idea to install a sign in clear sight that states that any persons entering the house or business is under surveillance. Make sure the camera is mounted properly and securely. Without proper mounting the camera may shift and change its focal point and possibly location, making it difficult to maintain adequate and accurate video surveillance. Outdoor cameras that are in plain sight are a great deterrent of criminal activity. Make sure if the camera is to be installed outside that it is designed to be used outdoors and that it is located in a position that will make it hard to reach or tamper with. Majority of wired cameras use what is called a BNC connector which is a small Quick-connect, Quick-disconnect for coaxial cables. BNC (Bayonet Neill Concelman) The term bayonet describes the connector’s style and Paul Neill and Carl Concelman were the two engineers who developed the connector .The BNC was originally designed for military use due to its quick connect/disconnect capabilities. The BNC connector is able to handle a max of 4 GHz signal strength with a high of 500 volts.
BNC Connector
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75 and 50 ohm BNC Connector
There are two major types of BNC connectors. The most common being the SR-50 and the SR-75 which are rated for 50 and 75 ohms respectively. One of the major benefits of the BNC connector is the flexibility of use. Though there are many different types of BNC connectors a vast majority of them are directly compatible. The industry standard cable for use in a security system is the RG59 Siamese cable. This cable is called a Siamese cable because it contains two parts one section of the cable carries the video signal while the other carries the power for the camera system. The camera’s typically run off of a 12v source.
Running cable can be a fairly easy or extremely difficult task depending on the location and requirements of job. For instance, running cable in an office environment is typically a fairly simple process, as in most offices having ceiling tiles that move easily out of the way and allow for simple and quick access to the cameras and overhead space for easy wire management. Important note to remember is that when moving and relocating ceiling tiles it is always important to make sure to only use your knuckles or gloved hands to lift and relocate the tiles, these tiles tend to get fingerprints extremely easy and are very difficult to clean. It is also very important to make slow and planned movements as these ceiling tiles tend to be very fragile and are not repairable, if one is dropped or damaged it will need to be replaced.
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You will also need to determine whether or not you will want to record the surveillance system, or if it will only need to be used as a live or direct view. Check with the customer prior to making your initial estimate to properly determine whether they need a DVR to record the camera system or if the job only requires a direct feed. A direct feed is good for usage for a front door or entrance to a gated area typically an area of low risk. The more common option of course is the DVR system as this allows for a live feed and the ability to record and maintain video information. Easily one of the most important parts of a Camera System is the DVR. There are many different types of DVR’s. The most common being a standalone DVR system. These DVR systems can range from 4-32 cameras each. Majority of the systems offer an online streaming option which allows you to view and record remotely from anywhere with an active internet connection. Many of the companies now offer smartphone applications that allow you to view the cameras from almost any Smartphone or tablet. Another type is the PC Based DVR which runs off a series of capture cards installed on a custom build computer. The PC based DVR’s tend to have a lot more flexibility for future upgrades. If these computers aren’t set up as a dedicated DVR then they may tend to be a bit more difficult to maintain. It is always recommended to have one system set up for dedicated DVR usage. The Pc based systems allow for much more storage capabilities but tend to cost much more than a typical standalone system. The average cost of a DVR suite for a pc will run roughly 4,000. One of the Pros of having that expensive and expansive of a system is the ability to utilize up to 64 cameras at once. With the upgradeability of a custom build DVR pc you are able to theoretically have all 64 cameras be at the highest resolution and record at that same level. Though the number of cameras used varies, the actual layout of the DVR systems are nearly identical between manufacturers. As seen in the DVR systems pictured they all have BNC connectors with many having at least 2 to 4 audio in connectors for the microphones. For video output majority of the systems utilize the VGA connector. Most DVR systems have a 500 gigabyte or bigger hard drive installed internally. This allows for anywhere from a week to a month of surveillance recording. Some of the newer systems which offer HD cameras are now starting to utilize the HDMI interface. HDMI which is an abbreviation
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for High-Definition Multimedia Interface is a unified audio and video interface. HDMI is able to transmit uncompressed video and audio data without the need for separate cables. Newer Systems are able to receive audio video and internet signal solely through the HDMI connection. Every DVR system that is able to connect to the internet for remote viewing will have an RJ-45 port. This utilizes the Cat-5e standard. You will need to follow the instructions given in the DVR systems user manual in order to set up the Remote Viewing as each system varies.
The typical DVR system includes the following parts. As shown to the right. The systems usually come with two power adaptors. The first which is used to power the DVR itself and the second which is used to supply the cameras with power. The “Camera Power Adaptor” typically has anywhere from 4 to 16 plugs on one side and another side which connects to the power adaptor. Each of these connectors will connect to the power that is on the “BNC/Power Cable”. The “Installation Hardware” is required for use when mounting to ceiling tiles or drywall as these materials tend to lose grip over time and the camera’s may become loose and fall out. The Installation anchors allow for the cameras to become far more secure.