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100-426: In physical security and information security , access control ( AC ) is the selective restriction of access to a place or other resource, while access management describes the process. The act of accessing may mean consuming, entering, or using. Permission to access a resource is called authorization . Access control on digital platforms is also termed admission control . The protection of external databases

200-882: A minimum illumination level of 0.2 foot-candles , measured horizontally at ground level, in the isolation zones and appropriate exterior areas within the protected area-". This is also the minimum illumination level specified in Table H–2 Minimum Night Firing Criteria of 10 CFR 73 Appendix H , for night firing. Per 10 CFR 73.46(b)(7) "-Tactical Response Team members, armed response personnel, and guards shall qualify and requalify, at least every 12 months, for day and night firing with assigned weapons in accordance with Appendix H-"; therefore on said respective shooting range [at night] per Appendix H, Table H-2 , "-all courses [shall have] 0.2 foot-candles at center mass of target area-" applicable to handguns , shotguns , and rifles. 1 foot-candle

300-448: A biometric input . There are three types (factors) of authenticating information: Passwords are a common means of verifying a user's identity before access is given to information systems. In addition, a fourth factor of authentication is now recognized: someone you know, whereby another person who knows you can provide a human element of authentication in situations where systems have been set up to allow for such scenarios. For example,

400-563: A GaAs p-n junction light emitter and an electrically isolated semiconductor photodetector. On August 8, 1962, Biard and Pittman filed a patent titled "Semiconductor Radiant Diode" based on their findings, which described a zinc-diffused p–n junction LED with a spaced cathode contact to allow for efficient emission of infrared light under forward bias . After establishing the priority of their work based on engineering notebooks predating submissions from G.E. Labs, RCA Research Labs, IBM Research Labs, Bell Labs , and Lincoln Lab at MIT ,

500-424: A card plus a PIN should always be used. Many access control credentials unique serial numbers are programmed in sequential order during manufacturing. Known as a sequential attack, if an intruder has a credential once used in the system they can simply increment or decrement the serial number until they find a credential that is currently authorized in the system. Ordering credentials with random unique serial numbers

600-657: A current source of a battery or a pulse generator and with a comparison to a variant, pure, crystal in 1953. Rubin Braunstein of the Radio Corporation of America reported on infrared emission from gallium arsenide (GaAs) and other semiconductor alloys in 1955. Braunstein observed infrared emission generated by simple diode structures using gallium antimonide (GaSb), GaAs, indium phosphide (InP), and silicon-germanium (SiGe) alloys at room temperature and at 77  kelvins . In 1957, Braunstein further demonstrated that

700-439: A deterrent when placed in highly visible locations and are useful for incident assessment and historical analysis. For example, if alarms are being generated and there is a camera in place, security personnel assess the situation via the camera feed. In instances when an attack has already occurred and a camera is in place at the point of attack, the recorded video can be reviewed. Although the term closed-circuit television (CCTV)

800-403: 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 do not provide records of the key used on any specific door, and the keys can be easily copied or transferred to an unauthorized person. When a mechanical key is lost or

900-444: A door left open longer than a specified length of time. The third most common security risk is natural disasters. In order to mitigate risk from natural disasters, the structure of the building, down to the quality of the network and computer equipment vital. From an organizational perspective, the leadership will need to adopt and implement an All Hazards Plan, or Incident Response Plan. The highlights of any incident plan determined by

1000-554: A glass window or lens to let the light out. Modern indicator LEDs are packed in transparent molded plastic cases, tubular or rectangular in shape, and often tinted to match the device color. Infrared devices may be dyed, to block visible light. More complex packages have been adapted for efficient heat dissipation in high-power LEDs . Surface-mounted LEDs further reduce the package size. LEDs intended for use with fiber optics cables may be provided with an optical connector. The first blue -violet LED, using magnesium-doped gallium nitride

1100-435: A high security prison or a military site may be inappropriate in an office, a home or a vehicle, although the principles are similar. The goal of deterrence methods is to convince potential attackers that a successful attack is unlikely due to strong defenses. The initial layer of security for a campus, building, office, or other physical space can use crime prevention through environmental design to deter threats. Some of

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1200-451: A host PC via Ethernet LAN or WAN. Advantages: Disadvantages: 7. IP readers. Readers are connected to a host PC via Ethernet LAN or WAN. Advantages: Disadvantages: The advantages and disadvantages of IP controllers apply to the IP readers as well. The most common security risk of intrusion through an access control system is by simply following a legitimate user through a door, and this

1300-494: A host PC via a serial RS-485 communication line (or via 20mA current loop in some older systems). External RS-232/485 converters or internal RS-485 cards have to be installed, as standard PCs do not have RS-485 communication ports. Advantages: Disadvantages: 2. Serial main and sub-controllers. All door hardware is connected to sub-controllers (a.k.a. door controllers or door interfaces). Sub-controllers usually do not make access decisions, and instead forward all requests to

1400-652: A key ring. Biometric technologies include fingerprint, facial recognition , iris recognition , retinal scan , voice, and hand geometry. The built-in biometric technologies found on newer smartphones can also be used as credentials in conjunction with access software running on mobile devices. In addition to older more traditional card access technologies, newer technologies such as near-field communication (NFC), Bluetooth low energy or Ultra-wideband (UWB) can also communicate user credentials to readers for system or building access. Components of an access control system include: Access control decisions are made by comparing

1500-568: A longer lifetime, improved physical robustness, smaller sizes, and faster switching. In exchange for these generally favorable attributes, disadvantages of LEDs include electrical limitations to low voltage and generally to DC (not AC) power, the inability to provide steady illumination from a pulsing DC or an AC electrical supply source, and a lesser maximum operating temperature and storage temperature. LEDs are transducers of electricity into light. They operate in reverse of photodiodes , which convert light into electricity. Electroluminescence as

1600-481: A loudspeaker. Intercepting the beam stopped the music. We had a great deal of fun playing with this setup." In September 1961, while working at Texas Instruments in Dallas , Texas , James R. Biard and Gary Pittman discovered near-infrared (900 nm) light emission from a tunnel diode they had constructed on a GaAs substrate. By October 1961, they had demonstrated efficient light emission and signal coupling between

1700-404: A means of further managing and monitoring access to mechanically keyed areas or access to certain small assets. Physical access control is a matter of who, where, and when. An access control system determines who is allowed to enter or exit, where they are allowed to exit or enter, and when they are allowed to enter or exit. Historically, this was partially accomplished through keys and locks. When

1800-557: A method for producing high-brightness blue LEDs using a new two-step process in 1991. In 2015, a US court ruled that three Taiwanese companies had infringed Moustakas's prior patent, and ordered them to pay licensing fees of not less than US$ 13 million. Two years later, in 1993, high-brightness blue LEDs were demonstrated by Shuji Nakamura of Nichia Corporation using a gallium nitride (GaN) growth process. These LEDs had efficiencies of 10%. In parallel, Isamu Akasaki and Hiroshi Amano of Nagoya University were working on developing

1900-514: A phenomenon was discovered in 1907 by the English experimenter Henry Joseph Round of Marconi Labs , using a crystal of silicon carbide and a cat's-whisker detector . Russian inventor Oleg Losev reported the creation of the first LED in 1927. His research was distributed in Soviet, German and British scientific journals, but no practical use was made of the discovery for several decades, partly due to

2000-567: A phosphor-silicon mixture on the LED using techniques such as jet dispensing, and allowing the solvents to evaporate, the LEDs are often tested, and placed on tapes for SMT placement equipment for use in LED light bulb production. Some "remote phosphor" LED light bulbs use a single plastic cover with YAG phosphor for one or several blue LEDs, instead of using phosphor coatings on single-chip white LEDs. Ce:YAG phosphors and epoxy in LEDs can degrade with use, and

2100-437: A piece of knowledge, or a facet of a person's physical being that enables an individual access to a given physical facility or computer-based information system. Typically, credentials can be something a person knows (such as a number or PIN), something they have (such as an access badge ), something they are (such as a biometric feature), something they do (measurable behavioural patterns), or some combination of these items. This

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2200-480: A psychological deterrent, by notifying intruders that their presence has been detected. In some U.S. jurisdictions, law enforcement will not respond to alarms from intrusion detection systems unless the activation has been verified by an eyewitness or video. Policies like this one have been created to combat the 94–99 percent rate of false alarm activation in the United States. Surveillance cameras can be

2300-503: A red light-emitting diode. GaAsP was the basis for the first wave of commercial LEDs emitting visible light. It was mass produced by the Monsanto and Hewlett-Packard companies and used widely for displays in calculators and wrist watches. M. George Craford , a former graduate student of Holonyak, invented the first yellow LED and improved the brightness of red and red-orange LEDs by a factor of ten in 1972. In 1976, T. P. Pearsall designed

2400-446: A security force that is trained in their use and maintenance, and which knows how to properly respond to breaches in security. Security personnel perform many functions: patrolling facilities, administering electronic access control, responding to alarms, and monitoring and analyzing video footage. LED A light-emitting diode ( LED ) is a semiconductor device that emits light when current flows through it. Electrons in

2500-481: A user by default have the same authority, this level of control is not fine-grained enough to satisfy the principle of least privilege , and arguably is responsible for the prevalence of malware in such systems (see computer insecurity ). In some models, for example the object-capability model , any software entity can potentially act as both subject and object. Physical security Physical security systems for protected facilities can be intended to: It

2600-413: A user may have their password, but have forgotten their smart card. In such a scenario, if the user is known to designated cohorts, the cohorts may provide their smart card and password, in combination with the extant factor of the user in question, and thus provide two factors for the user with the missing credential, giving three factors overall to allow access. A credential is a physical/tangible object,

2700-445: Is a prompt response when they are triggered. In the reconnaissance phase prior to an actual attack, some intruders will test the response time of security personnel to a deliberately tripped alarm system. By measuring the length of time it takes for a security team to arrive (if they arrive at all), the attacker can determine if an attack could succeed before authorities arrive to neutralize the threat. Loud audible alarms can also act as

2800-419: Is also common. An additional sub-layer of mechanical/electronic access control protection is reached by integrating a key management system to manage the possession and usage of mechanical keys to locks or property within a building or campus. Another form of access control ( procedural ) includes the use of policies, processes and procedures to manage the ingress into the restricted area. An example of this

2900-576: Is approximately 10.76 lux , therefore the minimum illumination requirements for the above sections also reflect 2.152 lux . Security alarms can be installed to alert security personnel when unauthorized access is attempted. Alarm systems work in tandem with physical barriers, mechanical systems, and security guards, serving to trigger a response when these other forms of security have been breached. They consist of sensors including perimeter sensors , motion sensors , contact sensors, and glass break detectors . However, alarms are only useful if there

3000-481: Is common, it is quickly becoming outdated as more video systems lose the closed circuit for signal transmission and are instead transmitting on IP camera networks. Video monitoring does not necessarily guarantee a human response. A human must be monitoring the situation in real time in order to respond in a timely manner; otherwise, video monitoring is simply a means to gather evidence for later analysis. However, technological advances like video analytics are reducing

3100-550: Is difficult but desirable since it takes advantage of existing semiconductor manufacturing infrastructure. It allows for the wafer-level packaging of LED dies resulting in extremely small LED packages. GaN is often deposited using metalorganic vapour-phase epitaxy (MOCVD), and it also uses lift-off . Even though white light can be created using individual red, green and blue LEDs, this results in poor color rendering , since only three narrow bands of wavelengths of light are being emitted. The attainment of high efficiency blue LEDs

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3200-486: Is difficult on silicon , while others, like the University of Cambridge, choose a multi-layer structure, in order to reduce (crystal) lattice mismatch and different thermal expansion ratios, to avoid cracking of the LED chip at high temperatures (e.g. during manufacturing), reduce heat generation and increase luminous efficiency. Sapphire substrate patterning can be carried out with nanoimprint lithography . GaN-on-Si

3300-573: Is directly adjacent to public sidewalks) or it may be aesthetically unacceptable (e.g. surrounding a shopping center with tall fences topped with razor wire); in this case, the outer security perimeter will be generally defined as the walls , windows and doors of the structure itself. Security lighting is another effective form of deterrence. Intruders are less likely to enter well-lit areas for fear of being seen. Doors, gates, and other entrances, in particular, should be well lit to allow close observation of people entering and exiting. When lighting

3400-499: Is essential to preserve digital security . Access control is considered to be a significant aspect of privacy that should be further studied. Access control policy (also access policy ) is part of an organization’s security policy . In order to verify the access control policy, organizations use an access control model. General security policies require designing or selecting appropriate security controls to satisfy an organization's risk appetite - access policies similarly require

3500-485: Is exit control, e.g. of a shop (checkout) or a country. The term access control refers to the practice of restricting entrance to a property, a building , or a room to authorized persons. Physical access control can be achieved by a human (a guard, bouncer, or receptionist), through mechanical means such as locks and keys, or through technological means such as access control systems like the mantrap . Within these environments, physical key management may also be employed as

3600-472: Is from levering a door open. This is relatively difficult on properly secured doors with strikes or high holding force magnetic locks. Fully implemented access control systems include forced door monitoring alarms. These vary in effectiveness, usually failing from high false positive alarms, poor database configuration, or lack of active intrusion monitoring. Most newer access control systems incorporate some type of door prop alarm to inform system administrators of

3700-427: Is known as multi-factor authentication . The typical credential is an access card or key-fob, and newer software can also turn users' smartphones into access devices. There are many card technologies including magnetic stripe, bar code, Wiegand , 125 kHz proximity, 26-bit card-swipe, contact smart cards, and contactless smart cards . Also available are key-fobs, which are more compact than ID cards, and attach to

3800-790: Is more apparent with higher concentrations of Ce:YAG in phosphor-silicone mixtures, because the Ce:YAG decomposes with use. The output of LEDs can shift to yellow over time due to degradation of the silicone. There are several variants of Ce:YAG, and manufacturers in many cases do not reveal the exact composition of their Ce:YAG offerings. Several other phosphors are available for phosphor-converted LEDs to produce several colors such as red, which uses nitrosilicate phosphors, and many other kinds of phosphor materials exist for LEDs such as phosphors based on oxides, oxynitrides, oxyhalides, halides, nitrides, sulfides, quantum dots, and inorganic-organic hybrid semiconductors. A single LED can have several phosphors at

3900-599: Is perceived as white light, with improved color rendering compared to wavelengths from the blue LED/YAG phosphor combination. The first white LEDs were expensive and inefficient. The light output then increased exponentially . The latest research and development has been propagated by Japanese manufacturers such as Panasonic and Nichia , and by Korean and Chinese manufacturers such as Samsung , Solstice, Kingsun, Hoyol and others. This trend in increased output has been called Haitz's law after Roland Haitz. Light output and efficiency of blue and near-ultraviolet LEDs rose and

4000-600: Is recommended to counter this threat. Finally, most electric locking hardware still has mechanical keys as a fail-over. Mechanical key locks are vulnerable to bumping . The need to know principle can be enforced with user access controls and authorization procedures and its objective is to ensure that only authorized individuals gain access to information or systems necessary to undertake their duties. In computer security , general access control includes authentication , authorization , and audit. A more narrow definition of access control would cover only access approval, whereby

4100-467: Is referred to as tailgating . Often the legitimate user will hold the door for the intruder. This risk can be minimized through security awareness training of the user population or more active means such as turnstiles. In very high-security applications this risk is minimized by using a sally port , sometimes called a security vestibule or mantrap, where operator intervention is required presumably to assure valid identification. The second most common risk

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4200-465: Is the deployment of security personnel conducting checks for authorized entry at predetermined points of entry. This form of access control is usually supplemented by the earlier forms of access control (i.e. mechanical and electronic access control), or simple devices such as physical passes. Security personnel play a central role in all layers of security. All of the technological systems that are employed to enhance physical security are useless without

4300-451: Is to use individual LEDs that emit three primary colors —red, green and blue—and then mix all the colors to form white light. The other is to use a phosphor material to convert monochromatic light from a blue or UV LED to broad-spectrum white light, similar to a fluorescent lamp . The yellow phosphor is cerium -doped YAG crystals suspended in the package or coated on the LED. This YAG phosphor causes white LEDs to appear yellow when off, and

4400-470: Is unavailable, will the readers use their internal database to make access decisions and record events. Semi-intelligent reader that have no database and cannot function without the main controller should be used only in areas that do not require high security. Main controllers usually support from 16 to 64 readers. All advantages and disadvantages are the same as the ones listed in the second paragraph. 4. Serial controllers with terminal servers. In spite of

4500-412: Is up to security designers, architects and analysts to balance security controls against risks, taking into account the costs of specifying, developing, testing, implementing, using, managing, monitoring and maintaining the controls, along with broader issues such as aesthetics , human rights , health and safety, and societal norms or conventions. Physical access security measures that are appropriate for

4600-526: The National Incident Management System must include Pre-incident planning, during incident actions, disaster recovery, and after-action review. Similar to levering is crashing through cheap partition walls. In shared tenant spaces, the divisional wall is a vulnerability. A vulnerability along the same lines is the breaking of sidelights. Spoofing locking hardware is fairly simple and more elegant than levering. A strong magnet can operate

4700-911: The Nobel Prize in Physics in 2014 for "the invention of efficient blue light-emitting diodes, which has enabled bright and energy-saving white light sources." In 1995, Alberto Barbieri at the Cardiff University Laboratory (GB) investigated the efficiency and reliability of high-brightness LEDs and demonstrated a "transparent contact" LED using indium tin oxide (ITO) on (AlGaInP/GaAs). In 2001 and 2002, processes for growing gallium nitride (GaN) LEDs on silicon were successfully demonstrated. In January 2012, Osram demonstrated high-power InGaN LEDs grown on silicon substrates commercially, and GaN-on-silicon LEDs are in production at Plessey Semiconductors . As of 2017, some manufacturers are using SiC as

4800-544: The U.S. patent office issued the two inventors the patent for the GaAs infrared light-emitting diode (U.S. Patent US3293513 ), the first practical LED. Immediately after filing the patent, Texas Instruments (TI) began a project to manufacture infrared diodes. In October 1962, TI announced the first commercial LED product (the SNX-100), which employed a pure GaAs crystal to emit an 890 nm light output. In October 1963, TI announced

4900-457: The human eye as a pure ( saturated ) color. Also unlike most lasers, its radiation is not spatially coherent , so it cannot approach the very high intensity characteristic of lasers . By selection of different semiconductor materials , single-color LEDs can be made that emit light in a narrow band of wavelengths from near-infrared through the visible spectrum and into the ultraviolet range. The required operating voltages of LEDs increase as

5000-451: The 3-subpixel model for digital displays. The technology uses a gallium nitride semiconductor that emits light of different frequencies modulated by voltage changes. A prototype display achieved a resolution of 6,800 PPI or 3k x 1.5k pixels. In a light-emitting diode, the recombination of electrons and electron holes in a semiconductor produces light (be it infrared, visible or UV), a process called " electroluminescence ". The wavelength of

5100-479: The RS-485-related advantages and disadvantages also apply. 5. Network-enabled main controllers. The topology is nearly the same as described in the second and third paragraphs. The same advantages and disadvantages apply, but the on-board network interface offers a couple of valuable improvements. Transmission of configuration and user data to the main controllers is faster, and may be done in parallel. This makes

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5200-413: The access control list, the control panel operates a relay that in turn unlocks the resource. The control panel also ignores an opening signal to prevent an alarm. Often the reader provides feedback, such as a flashing red LED for an access denied and a flashing green LED for an access granted. The above description illustrates a single factor transaction. Credentials can be passed around, thus subverting

5300-440: The access control list. For example, Alice has access rights to the server room , but Bob does not. Alice either gives Bob her credential, or Bob takes it; he now has access to the server room. To prevent this, two-factor authentication can be used. In a two factor transaction, the presented credential and a second factor are needed for access to be granted; another factor can be a PIN, a second credential, operator intervention, or

5400-548: The amount of work required for video monitoring as security personnel can be automatically notified of potential security events. Access control methods are used to monitor and control traffic through specific access points and areas of the secure facility. This is done using a variety of methods, including CCTV surveillance , identification cards , security guards , biometric readers , locks , doors, turnstiles and gates . Mechanical access control systems include turnstiles, gates, doors, and locks. Key control of

5500-797: The blending of the colors. Since LEDs have slightly different emission patterns, the color balance may change depending on the angle of view, even if the RGB sources are in a single package, so RGB diodes are seldom used to produce white lighting. Nonetheless, this method has many applications because of the flexibility of mixing different colors, and in principle, this mechanism also has higher quantum efficiency in producing white light. There are several types of multicolor white LEDs: di- , tri- , and tetrachromatic white LEDs. Several key factors that play among these different methods include color stability, color rendering capability, and luminous efficacy. Often, higher efficiency means lower color rendering, presenting

5600-1083: The cladding and quantum well layers for ultraviolet LEDs, but these devices have not yet reached the level of efficiency and technological maturity of InGaN/GaN blue/green devices. If unalloyed GaN is used in this case to form the active quantum well layers, the device emits near-ultraviolet light with a peak wavelength centred around 365 nm. Green LEDs manufactured from the InGaN/GaN system are far more efficient and brighter than green LEDs produced with non-nitride material systems, but practical devices still exhibit efficiency too low for high-brightness applications. With AlGaN and AlGaInN , even shorter wavelengths are achievable. Near-UV emitters at wavelengths around 360–395 nm are already cheap and often encountered, for example, as black light lamp replacements for inspection of anti- counterfeiting UV watermarks in documents and bank notes, and for UV curing . Substantially more expensive, shorter-wavelength diodes are commercially available for wavelengths down to 240 nm. As

5700-661: The control panel. The spokes communicate through a serial connection; usually RS-485. Some manufactures are pushing the decision making to the edge by placing a controller at the door. The controllers are IP enabled, and connect to a host and database using standard networks Access control readers may be classified by the functions they are able to perform: Some readers may have additional features such as an LCD and function buttons for data collection purposes (i.e. clock-in/clock-out events for attendance reports), camera/speaker/microphone for intercom, and smart card read/write support. 1. Serial controllers. Controllers are connected to

5800-417: The cost of reliable devices fell. This led to relatively high-power white-light LEDs for illumination, which are replacing incandescent and fluorescent lighting. Experimental white LEDs were demonstrated in 2014 to produce 303 lumens per watt of electricity (lm/W); some can last up to 100,000 hours. Commercially available LEDs have an efficiency of up to 223 lm/W as of 2018. A previous record of 135 lm/W

5900-405: The credential presented. When access is granted, the resource is unlocked for a predetermined time and the transaction is recorded. When access is refused, the resource remains locked and the attempted access is recorded. The system will also monitor the resource and alarm if the resource is forcefully unlocked or held open too long after being unlocked. When a credential is presented to a reader,

6000-440: The credentials to an access control list. This look-up can be done by a host or server, by an access control panel, or by a reader. The development of access control systems has observed a steady push of the look-up out from a central host to the edge of the system, or the reader. The predominant topology circa 2009 is hub and spoke with a control panel as the hub, and the readers as the spokes. The look-up and control functions are by

6100-447: The door. Access cards themselves have proven vulnerable to sophisticated attacks. Enterprising hackers have built portable readers that capture the card number from a user's proximity card. The hacker simply walks by the user, reads the card, and then presents the number to a reader securing the door. This is possible because card numbers are sent in the clear, no encryption being used. To counter this, dual authentication methods, such as

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6200-1075: The earliest LEDs emitted low-intensity infrared (IR) light. Infrared LEDs are used in remote-control circuits, such as those used with a wide variety of consumer electronics. The first visible-light LEDs were of low intensity and limited to red. Early LEDs were often used as indicator lamps, replacing small incandescent bulbs , and in seven-segment displays . Later developments produced LEDs available in visible , ultraviolet (UV), and infrared wavelengths with high, low, or intermediate light output, for instance, white LEDs suitable for room and outdoor lighting. LEDs have also given rise to new types of displays and sensors, while their high switching rates are useful in advanced communications technology with applications as diverse as aviation lighting , fairy lights , strip lights , automotive headlamps , advertising, general lighting , traffic signals , camera flashes, lighted wallpaper , horticultural grow lights , and medical devices. LEDs have many advantages over incandescent light sources, including lower power consumption,

6300-520: The electricity is cut off. The introduction of low-voltage LED-based lighting products has enabled new security capabilities, such as instant-on or strobing, while substantially reducing electrical consumption. For nuclear power plants in the United States (U.S.) , per the U.S. Nuclear Regulatory Commission (NRC) , 10 CFR Part 73 , [security] lighting is mentioned four times. The most notable mentioning contained in 10 CFR 73.55(i)(6) Illumination , which clearly identifies that licensees "-shall provide

6400-539: The emitted wavelengths become shorter (higher energy, red to blue), because of their increasing semiconductor band gap. Blue LEDs have an active region consisting of one or more InGaN quantum wells sandwiched between thicker layers of GaN, called cladding layers. By varying the relative In/Ga fraction in the InGaN quantum wells, the light emission can in theory be varied from violet to amber. Aluminium gallium nitride (AlGaN) of varying Al/Ga fraction can be used to manufacture

6500-504: The entities that can perform actions on the system are called subjects , and the entities representing resources to which access may need to be controlled are called objects (see also Access Control Matrix ). Subjects and objects should both be considered as software entities, rather than as human users: any human users can only have an effect on the system via the software entities that they control. Although some systems equate subjects with user IDs , so that all processes started by

6600-491: The field of luminescence with research on radium . Hungarian Zoltán Bay together with György Szigeti patenting a lighting device in Hungary in 1939 based on silicon carbide, with an option on boron carbide, that emitted white, yellowish white, or greenish white depending on impurities present. Kurt Lehovec , Carl Accardo, and Edward Jamgochian explained these first LEDs in 1951 using an apparatus employing SiC crystals with

6700-602: The first commercial hemispherical LED, the SNX-110. In the 1960s, several laboratories focused on LEDs that would emit visible light. A particularly important device was demonstrated by Nick Holonyak on October 9, 1962, while he was working for General Electric in Syracuse, New York . The device used the semiconducting alloy gallium phosphide arsenide (GaAsP). It was the first semiconductor laser to emit visible light, albeit at low temperatures. At room temperature it still functioned as

6800-518: The first commercially available blue LED, based on the indirect bandgap semiconductor, silicon carbide (SiC). SiC LEDs had very low efficiency, no more than about 0.03%, but did emit in the blue portion of the visible light spectrum. In the late 1980s, key breakthroughs in GaN epitaxial growth and p-type doping ushered in the modern era of GaN-based optoelectronic devices. Building upon this foundation, Theodore Moustakas at Boston University patented

6900-721: The first high-brightness, high-efficiency LEDs for optical fiber telecommunications by inventing new semiconductor materials specifically adapted to optical fiber transmission wavelengths. Until 1968, visible and infrared LEDs were extremely costly, on the order of US$ 200 per unit, and so had little practical use. The first commercial visible-wavelength LEDs used GaAsP semiconductors and were commonly used as replacements for incandescent and neon indicator lamps , and in seven-segment displays , first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as calculators, TVs, radios, telephones, as well as watches. The Hewlett-Packard company (HP)

7000-457: The grounds of a facility, widely distributed low-intensity lighting is generally superior to small patches of high-intensity lighting, because the latter can have a tendency to create blind spots for security personnel and CCTV cameras. It is important to place lighting in a manner that makes it difficult to tamper with (e.g. suspending lights from tall poles), and to ensure that there is a backup power supply so that security lights will not go out if

7100-407: The important GaN deposition on sapphire substrates and the demonstration of p-type doping of GaN. This new development revolutionized LED lighting, making high-power blue light sources practical, leading to the development of technologies like Blu-ray . Nakamura was awarded the 2006 Millennium Technology Prize for his invention. Nakamura, Hiroshi Amano , and Isamu Akasaki were awarded

7200-530: The key holder is no longer authorized to use the protected area, the locks must be re-keyed. Electronic access control (EAC) uses computers to solve the limitations of mechanical locks and keys. It is particularly difficult to guarantee identification (a critical component of authentication ) with mechanical locks and keys. A wide range of credentials can be used to replace mechanical keys, allowing for complete authentication, authorization, and accounting . The electronic access control system grants access based on

7300-417: The light depends on the energy band gap of the semiconductors used. Since these materials have a high index of refraction, design features of the devices such as special optical coatings and die shape are required to efficiently emit light. Unlike a laser , the light emitted from an LED is neither spectrally coherent nor even highly monochromatic . Its spectrum is sufficiently narrow that it appears to

7400-420: The light produced is engineered to suit the human eye. Because of metamerism , it is possible to have quite different spectra that appear white. The appearance of objects illuminated by that light may vary as the spectrum varies. This is the issue of color rendition, quite separate from color temperature. An orange or cyan object could appear with the wrong color and much darker as the LED or phosphor does not emit

7500-547: The locks becomes a problem with large user populations and any user turnover. Keys quickly become unmanageable, often forcing the adoption of electronic access control. Electronic access control systems provide secure access to buildings or facilities by controlling who can enter and exit. Some aspects of these systems can include: Electronic access control uses credential readers, advanced software, and electrified locks to provide programmable, secure access management for facilities. Integration of cameras, alarms and other systems

7600-400: The main controllers. Main controllers usually support from 16 to 32 sub-controllers. Advantages: Disadvantages: 3. Serial main controllers & intelligent readers. All door hardware is connected directly to intelligent or semi-intelligent readers. Readers usually do not make access decisions, and forward all requests to the main controller. Only if the connection to the main controller

7700-538: The most common examples are also the most basic: warning signs or window stickers, fences , vehicle barriers, vehicle height-restrictors, restricted access points, security lighting and trenches. For example, tall fencing, topped with barbed wire , razor wire or metal spikes are often emplaced on the perimeter of a property, generally with some type of signage that warns people not to attempt entry. However, in some facilities imposing perimeter walls or fencing will not be possible (e.g. an urban office building that

7800-464: The organization to design or select access controls. Geographical access control may be enforced by personnel (e.g. border guard , bouncer , ticket checker), or with a device such as a turnstile . There may be fences to avoid circumventing this access control. An alternative of access control in the strict sense (physically controlling access itself) is a system of checking authorized presence, see e.g. Ticket controller (transportation) . A variant

7900-445: The phosphors, the Ce:YAG phosphor converts blue light to green and red (yellow) light, and the PFS phosphor converts blue light to red light. The color, emission spectrum or color temperature of white phosphor converted and other phosphor converted LEDs can be controlled by changing the concentration of several phosphors that form a phosphor blend used in an LED package. The 'whiteness' of

8000-599: The photosensitivity of microorganisms approximately matches the absorption spectrum of DNA , with a peak at about 260 nm, UV LED emitting at 250–270 nm are expected in prospective disinfection and sterilization devices. Recent research has shown that commercially available UVA LEDs (365 nm) are already effective disinfection and sterilization devices. UV-C wavelengths were obtained in laboratories using aluminium nitride (210 nm), boron nitride (215 nm) and diamond (235 nm). There are two primary ways of producing white light-emitting diodes. One

8100-408: The rapid development and increasing use of computer networks, access control manufacturers remained conservative, and did not rush to introduce network-enabled products. When pressed for solutions with network connectivity, many chose the option requiring less efforts: addition of a terminal server , a device that converts serial data for transmission via LAN or WAN. Advantages: Disadvantages: All

8200-406: The reader sends the credential's information, usually a number, to a control panel, a highly reliable processor. The control panel compares the credential's number to an access control list, grants or denies the presented request, and sends a transaction log to a database . When access is denied based on the access control list , the door remains locked. If there is a match between the credential and

8300-421: The rudimentary devices could be used for non-radio communication across a short distance. As noted by Kroemer Braunstein "…had set up a simple optical communications link: Music emerging from a record player was used via suitable electronics to modulate the forward current of a GaAs diode. The emitted light was detected by a PbS diode some distance away. This signal was fed into an audio amplifier and played back by

8400-480: The same time. Some LEDs use phosphors made of glass-ceramic or composite phosphor/glass materials. Alternatively, the LED chips themselves can be coated with a thin coating of phosphor-containing material, called a conformal coating. The temperature of the phosphor during operation and how it is applied limits the size of an LED die. Wafer-level packaged white LEDs allow for extremely small LEDs. In 2024, QPixel introduced as polychromatic LED that could replace

8500-442: The semiconductor recombine with electron holes , releasing energy in the form of photons . The color of the light (corresponding to the energy of the photons) is determined by the energy required for electrons to cross the band gap of the semiconductor. White light is obtained by using multiple semiconductors or a layer of light-emitting phosphor on the semiconductor device. Appearing as practical electronic components in 1962,

8600-505: The solenoid controlling bolts in electric locking hardware. Motor locks, more prevalent in Europe than in the US, are also susceptible to this attack using a doughnut-shaped magnet. It is also possible to manipulate the power to the lock either by removing or adding current, although most Access Control systems incorporate battery back-up systems and the locks are almost always located on the secure side of

8700-408: The space between the crystals allow some blue light to pass through in LEDs with partial phosphor conversion. Alternatively, white LEDs may use other phosphors like manganese(IV)-doped potassium fluorosilicate (PFS) or other engineered phosphors. PFS assists in red light generation, and is used in conjunction with conventional Ce:YAG phosphor. In LEDs with PFS phosphor, some blue light passes through

8800-547: The subsequent device Pankove and Miller built, the first actual gallium nitride light-emitting diode, emitted green light. In 1974 the U.S. Patent Office awarded Maruska, Rhines, and Stanford professor David Stevenson a patent for their work in 1972 (U.S. Patent US3819974 A ). Today, magnesium-doping of gallium nitride remains the basis for all commercial blue LEDs and laser diodes . In the early 1970s, these devices were too dim for practical use, and research into gallium nitride devices slowed. In August 1989, Cree introduced

8900-474: The substrate for LED production, but sapphire is more common, as it has the most similar properties to that of gallium nitride, reducing the need for patterning the sapphire wafer (patterned wafers are known as epi wafers). Samsung , the University of Cambridge , and Toshiba are performing research into GaN on Si LEDs. Toshiba has stopped research, possibly due to low yields. Some opt for epitaxy , which

9000-561: The system makes a decision to grant or reject an access request from an already authenticated subject, based on what the subject is authorized to access. Authentication and access control are often combined into a single operation, so that access is approved based on successful authentication, or based on an anonymous access token. Authentication methods and tokens include passwords, biometric analysis, physical keys, electronic keys and devices, hidden paths, social barriers, and monitoring by humans and automated systems. In any access-control model,

9100-409: The system more responsive, and does not interrupt normal operations. No special hardware is required in order to achieve redundant host PC setup: in the case that the primary host PC fails, the secondary host PC may start polling network controllers. The disadvantages introduced by terminal servers (listed in the fourth paragraph) are also eliminated. 6. IP controllers . Controllers are connected to

9200-569: The team at Fairchild led by optoelectronics pioneer Thomas Brandt to achieve the needed cost reductions. LED producers have continued to use these methods as of about 2009. The early red LEDs were bright enough for use as indicators, as the light output was not enough to illuminate an area. Readouts in calculators were so small that plastic lenses were built over each digit to make them legible. Later, other colors became widely available and appeared in appliances and equipment. Early LEDs were packaged in metal cases similar to those of transistors, with

9300-461: The very inefficient light-producing properties of silicon carbide, the semiconductor Losev used. In 1936, Georges Destriau observed that electroluminescence could be produced when zinc sulphide (ZnS) powder is suspended in an insulator and an alternating electrical field is applied to it. In his publications, Destriau often referred to luminescence as Losev-Light. Destriau worked in the laboratories of Madame Marie Curie , also an early pioneer in

9400-532: The wavelength it reflects. The best color rendition LEDs use a mix of phosphors, resulting in less efficiency and better color rendering. The first white light-emitting diodes (LEDs) were offered for sale in the autumn of 1996. Nichia made some of the first white LEDs which were based on blue LEDs with Ce:YAG phosphor. Ce:YAG is often grown using the Czochralski method . Mixing red, green, and blue sources to produce white light needs electronic circuits to control

9500-618: Was achieved by Nichia in 2010. Compared to incandescent bulbs, this is a huge increase in electrical efficiency, and even though LEDs are more expensive to purchase, overall lifetime cost is significantly cheaper than that of incandescent bulbs. The LED chip is encapsulated inside a small, plastic, white mold although sometimes an LED package can incorporate a reflector. It can be encapsulated using resin ( polyurethane -based), silicone, or epoxy containing (powdered) Cerium-doped YAG phosphor particles. The viscosity of phosphor-silicon mixtures must be carefully controlled. After application of

9600-415: Was engaged in research and development (R&D) on practical LEDs between 1962 and 1968, by a research team under Howard C. Borden, Gerald P. Pighini at HP Associates and HP Labs . During this time HP collaborated with Monsanto Company on developing the first usable LED products. The first usable LED products were HP's LED display and Monsanto's LED indicator lamp , both launched in 1968. Monsanto

9700-433: Was made at Stanford University in 1972 by Herb Maruska and Wally Rhines , doctoral students in materials science and engineering. At the time Maruska was on leave from RCA Laboratories , where he collaborated with Jacques Pankove on related work. In 1971, the year after Maruska left for Stanford, his RCA colleagues Pankove and Ed Miller demonstrated the first blue electroluminescence from zinc-doped gallium nitride, though

9800-443: Was quickly followed by the development of the first white LED . In this device a Y 3 Al 5 O 12 :Ce (known as " YAG " or Ce:YAG phosphor) cerium -doped phosphor coating produces yellow light through fluorescence . The combination of that yellow with remaining blue light appears white to the eye. Using different phosphors produces green and red light through fluorescence. The resulting mixture of red, green and blue

9900-567: Was the first intelligent LED display, and was a revolution in digital display technology, replacing the Nixie tube and becoming the basis for later LED displays. In the 1970s, commercially successful LED devices at less than five cents each were produced by Fairchild Optoelectronics. These devices employed compound semiconductor chips fabricated with the planar process (developed by Jean Hoerni , ). The combination of planar processing for chip fabrication and innovative packaging methods enabled

10000-479: Was the first organization to mass-produce visible LEDs, using Gallium arsenide phosphide (GaAsP) in 1968 to produce red LEDs suitable for indicators. Monsanto had previously offered to supply HP with GaAsP, but HP decided to grow its own GaAsP. In February 1969, Hewlett-Packard introduced the HP Model 5082-7000 Numeric Indicator, the first LED device to use integrated circuit (integrated LED circuit ) technology. It

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