Biometric Applications
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Book-Understanding Biometrics
Introduction to Biometrics
Authentication Technologies
History of Biometrics
Types of Biometrics
Biometric System Model
Biometric Applications Characterization
Biometric Applications
Biometric Domains
What types of biometrics exist?
How to evaluate biometric systems
Who is evaluating the biometric software around the world
Biometric Standards and Interoperability issues
Fingerprint SDK 2009 Developer's Manual
Fingerprint Readers Installation
Fingerprint SDK Java
Griaule AFIS 2.0 Developer's Manual
Griaule WSQ 1.2 Developer's Manual
ICAO Face 2008 SDK Developer´s Manual
Fingerprint recognition
From Wikipedia, the free encyclopedia
Fingerprint recognition or fingerprint authentication refers to the automated method of verifying a
match between two human fingerprints. Fingerprints are one of many forms of biometricsused
to identify individuals and verify their identity. This article touches on two major classes
of algorithms (minutia and pattern) and four sensor designs (optical, ultrasonic, passive capacitance, and
active capacitance).
Contents
[hide]



1 Background
o
1.1 Patterns
o
1.2 Minutia features
2 Fingerprint sensors
o
2.1 Optical
o
2.2 Ultrasonic
o
2.3 Capacitance

2.3.1 Passive capacitance

2.3.2 Active capacitance
3 Algorithms
o
3.1 Pattern-based (or image-based) algorithms

4 See also

5 References

6 Reference

7 External links
[edit]Background
The analysis of fingerprints for matching purposes generally requires the comparison of several features of
the print pattern. These include patterns, which are aggregate characteristics of ridges, and minutia points,
which are unique features found within the patterns.[1] It is also necessary to know the structure and
properties of human skin in order to successfully employ some of the imaging technologies.
[edit]Patterns
The three basic patterns of fingerprint ridges are the arch, loop, and whorl:

arch: The ridges enter from one side of the finger, rise in the center forming an arc, and then exit the
other side of the finger.

loop: The ridges enter from one side of a finger, form a curve, and then exit on that same side.

whorl: Ridges form circularly around a central point on the finger.
Scientists have found that family members often share the same general fingerprint patterns, leading to the
belief that these patterns are inherited.[2]
The whorl pattern.
The arch pattern.
The loop pattern.
[edit]Minutia
features
The major Minutia features of fingerprint ridges are: ridge ending, bifurcation, and short ridge (or dot). The
ridge ending is the point at which a ridge terminates. Bifurcations are points at which a single ridge splits
into two ridges. Short ridges (or dots) are ridges which are significantly shorter than the average ridge
length on the fingerprint. Minutiae and patterns are very important in the analysis of fingerprints since no
two fingers have been shown to be identical.[3]
Ridge ending.
Bifurcation.
[edit]Fingerprint
Short Ridge (Dot).
sensors
A fingerprint sensor is an electronic device used to capture a digital image of the fingerprint pattern. The
captured image is called a live scan. This live scan is digitally processed to create a biometric template (a
collection of extracted features) which is stored and used for matching. This is an overview of some of the
more commonly used fingerprint sensor technologies.
[edit]Optical
Optical fingerprint imaging involves capturing a digital image of the print using visible light. This type of
sensor is, in essence, a specialized digital camera. The top layer of the sensor, where the finger is placed,
is known as the touch surface. Beneath this layer is a light-emitting phosphor layer which illuminates the
surface of the finger. The light reflected from the finger passes through the phosphor layer to an array
of solid state pixels (a charge-coupled device) which captures a visual image of the fingerprint. A scratched
or dirty touch surface can cause a bad image of the fingerprint. A disadvantage of this type of sensor is the
fact that the imaging capabilities are affected by the quality of skin on the finger. For instance, a dirty or
marked finger is difficult to image properly. Also, it is possible for an individual to erode the outer layer of
skin on the fingertips to the point where the fingerprint is no longer visible. It can also be easily fooled by an
image of a fingerprint if not coupled with a "live finger" detector. However, unlike capacitive sensors, this
sensor technology is not susceptible to electrostatic discharge damage.
[4]
Fingerprints can be read from a distance.[1]
[edit]Ultrasonic
Ultrasonic sensors make use of the principles of medical ultrasonography in order to create visual images
of the fingerprint. Unlike optical imaging, ultrasonic sensors use very high frequency sound waves to
penetrate the epidermal layer of skin. The sound waves are generated using piezoelectric transducers and
reflected energy is also measured using piezoelectric materials. Since the dermal skin layer exhibits the
same characteristic pattern of the fingerprint, the reflected wave measurements can be used to form an
image of the fingerprint. This eliminates the need for clean, undamaged epidermal skin and a clean sensing
surface.[5]
[edit]Capacitance
Capacitance sensors utilize the principles associated with capacitance in order to form fingerprint images.
In this method of imaging, the sensor array pixels each act as one plate of a parallel-plate capacitor, the
dermal layer (which is electrically conductive) acts as the other plate, and the non-conductive epidermal
layer acts as a dielectric.
[edit]Passive capacitance
A passive capacitance sensor uses the principle outlined above to form an image of the fingerprint patterns
on the dermal layer of skin. Each sensor pixel is used to measure the capacitance at that point of the array.
The capacitance varies between the ridges and valleys of the fingerprint due to the fact that the volume
between the dermal layer and sensing element in valleys contains an air gap. The dielectric constant of the
epidermis and the area of the sensing element are known values. The measured capacitance values are
then used to distinguish between fingerprint ridges and valleys.[6]
[edit]Active capacitance
Active capacitance sensors use a charging cycle to apply a voltage to the skin before measurement takes
place. The application of voltage charges the effective capacitor. The electric field between the finger and
sensor follows the pattern of the ridges in the dermal skin layer. On the discharge cycle, the voltage across
the dermal layer and sensing element is compared against a reference voltage in order to calculate the
capacitance. The distance values are then calculated mathematically, and used to form an image of the
fingerprint.[7] Active capacitance sensors measure the ridge patterns of the dermal layer like the ultrasonic
method. Again, this eliminates the need for clean, undamaged epidermal skin and a clean sensing
surface.[7]
[edit]Algorithms
Matching algorithms are used to compare previously stored templates of fingerprints against candidate
fingerprints for authentication purposes. In order to do this either the original image must be directly
compared with the candidate image or certain features must be compared.[8]
[edit]Pattern-based
(or image-based) algorithms
Pattern based algorithms compare the basic fingerprint patterns (arch, whorl, and loop) between a
previously stored template and a candidate fingerprint. This requires that the images be aligned in the
same orientation. To do this, the algorithm finds a central point in the fingerprint image and centers on that.
In a pattern-based algorithm, the template contains the type, size, and orientation of patterns within the
aligned fingerprint image. The candidate fingerprint image is graphically compared with the template to
determine the degree to which they match.[9]
[edit]See

Fingerprint Verification Competition

Online Fingerprint Identification SDK, Saurabh

Biometrics

Authentication

Fingerprint

Minutiae

Feature extraction

Skin

Heredity

Medical ultrasonography

Piezoelectricity

Biometric technology in access control

Finger Vein recognition

Iris recognition
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Return codes
REX Quick Start Guide
User Manual for Biometric Network Logon
User Manual for GrFinger Desktop Identity
User Manual for GrFinger Desktop Login
User Manual for REX Device
User Manual for REX Identity
User Manual for REX2006 SDK
Event constants
also
In the last years has considerably increased the area of application of biometrics and it's expected that
in the near future, we will use biometry many times in our dayly activities such as getting in the car,
openning the door of our house, accessing to our bank acount, shoping by internet, accessing to our
PDA, mobil phone, laptops, etc. Depending of where the biometrics is deployed, the applications can be
categorized in the following five main groups: forensic, government, commercial, health-care and
traveling and immigration. However, some applications are common to these groups such as physical
access, PC/network access, time and attendance, etc.
Forensic
The use of biometric in the law enforcement and forensic is more known and from long date, it is used
mainly for identification of criminals. In particular, the AFIS (automatic fingerprint identification system)
has been used for this purpose. Lately the facial-scan technology (mug shots) is being also used for
identification of suspects. Another possible application is the verification of persons of home arrest, a
voice-scan is an attractive solution for this problem. The typical application are:
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Identification of criminals- collecting the evidence in the scene of crime (e.g., fingerprints) it is
possible to compare with data of suspects or make a search in the database of criminals.
Surveillance --using cameras one can monitor the very busy places such as stadiums, airports,
meetings, etc. Looking in the crowds for suspect, based on the face recognition biometric, using a
images (e.g., mug shots) database of wanted persons or criminals. Since the events of September
11, 2001, the interest in biometric surveillance has increased dramatically, especially for air travel
applications. Currently there are many cameras monitoring crowds at airports for detecting wanted
terrorists.
Corrections -This refers to the treatment of offenders (criminals) through a system of penal
incarceration, rehabilitation, probation, and parole, or the administrative system by which these are
effectuated. Is this cases a biometric system can avoid the possibility of accidentally releasing the
wrong prisoner, or to ensure that people leaving the facilities are really visitors and not inmates.
Probation and home arrest - biometric can also be used for post-release programs (conditional
released) to ensure the fulfilment of the probation, parole and home detention terms.
Government
There are many application of the biometry in the government sector. An AFIS is the primary system
used for locating duplicates enrolls in benefits systems, electronic voting for local or national elections,
driver's license emission, etc. The typical application are:
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National Identification Cards - the idea is to include digital biometric information in the national
identification card. This is the most ambitious biometric program, since the identification must be
performed in a large-scale database, containing hundred of millions samples, corresponding to the
whole population of one country. This kind of cards can be used for multiple purposes such as
controlling the collection of benefits, avoiding duplicates of voter registration and drivers license
emission. All this applications are primarily based on finger-scan and AFIS technology, however it is
possible that facial-scan and iris-scan technology could be used in the future.
Voter ID and Elections - while the biometric national ID card is still in project, in many countries
are already used the biometry for the control of voting and voter registration for the national or
regional elections. During the registration of voter, the biometric data is captured and stored in the
card and in the database for the later use during the voting. The purpose is to prevent the duplicate
registration and voting.
Driver's licenses - In many countries the driver license is also used as identification document,
therefore it is important to prevent the duplicate emission of the driver license under different
name. With the use of biometric this problem can be eliminated. however it is important that the
data must be shared between state, because in some country such as United States, the license are
controlled at the states as opposed to the federal level.
Benefits Distribution (social service) - the use of biometry in benefits distribution prevents
fraud and abuse of the government benefits programs. Ensuring that the legitimate recipients have


a quick and convenient access to the benefits such as unemployment, health care and social
security benefits.
Employee authentication - The government use of biometric for PC, network, and data access is
also important for security of building and protection of information. Below are more detailed this
kind of applications also used in commercial sector.
Military programs - the military has long been interested in biometrics and the technology has
enjoyed extensive support from the national security community.
Commercial
Banking and financial services represent enormous growth areas for biometric technology, with
many deployments currently functioning and pilot project announced frequently. Some applications
in this sector are:
o
o
o
o
o
o
o
o
o
Account access - The use of biometric for the access to the account in the bank allows to keep
definitive and auditable records of account access by employees and customers. Using biometry
the the customers can access accounts and employees can log into their workstations.
ATMs - the use of biometric in the ATM transaction allows more security,
Expanded Service Kiosks - A more receptive market for biometrics may be special purpose
kiosks, using biometric verification to allow a greater variety of financial transaction than are
currently available though standard ATMs.
Online banking - Internet based account access is already widely used in many places, the
inclusion of biometric will make more secure this type of transactions from home. Currently,
there are many pilot programs using biometric in home banking.
Telephony transaction - Voice-scan biometric can be used to make more secure the
telephone-based transactions. In this type of application, when the costumer calls to make a
transaction, a biometric system will authenticate the customer's identity based on his or her
voice with no need of any additional device.
PC/Network access - The use of biometric log-in to local PCs or remotely through network
increase the security of the overall system keeping more protected the valuable information.
Physical access - the biometric is widely used for controlling the access to building or
restricted areas.
E-commerce - biometric e-commerce is the use of biometrics to verify of identity of the
individual conduction remote transaction for goods or services
Time and attendance monitoring - In this sector the biometrics is used for controlling the
presence of the individuals in a determine area. For example for controlling the time sheet of
the employees or the presence of students at the classroom
Health Care
The applications in this sector includes the use of biometrics to identify or verify the identity of
individuals interacting with a health-care entity or acting in the capacity of health-care employee or
professional. The main aim of biometrics is to prevent fraud, protect the patient information and
control the sell of pharmaceutical products. Some typical application are:
o
o
o
PC/Network Access - the biometrics are used to control a secure access of the employees to
the hospital network, primarily, in order to protect the patient information,
Access to personal information - Using biometrics, the medical patient information maybe
stored on smart card or secure networks, this will enable the access of the patients to their
personal information.
Patient identification - In case of emergency, when a patient does not have identification
document and is unable no communicate, biometric identification may be a good alternative to
identify.
Travel and Immigration
The application in this sector includes the use of biometrics to identify or verify the identity of
individual interacting during the course of travel, with a travel or immigration entity or acting in the
capacity of travel or immigration employee. Typical application are:
o
o
o
o
Air travel - In many airport are already used a biometric system in order to reduce the
inspection processing time for authorized travelers.
Border crossing - The use of biometrics to control the travelers crossing the national or state
border is increasing, specially in regions with high volume of travelers or illegal immigrants.
Employee access - Several airport use biometric to control the physical access of employees to
secure areas.
Passports - Some country already issues passports with biometric information on a barcode or
smart chips. The use of biometrics prevent the emission of multiple passports for the same
person and also facilitates
Fingerprint recognition
From Wikipedia, the free encyclopedia
Fingerprint recognition or fingerprint authentication refers to the automated method of verifying a
match between two human fingerprints. Fingerprints are one of many forms of biometricsused
to identify individuals and verify their identity. This article touches on two major classes
of algorithms (minutia and pattern) and four sensor designs (optical, ultrasonic, passive capacitance, and
active capacitance).
Contents
[hide]



1 Background
o
1.1 Patterns
o
1.2 Minutia features
2 Fingerprint sensors
o
2.1 Optical
o
2.2 Ultrasonic
o
2.3 Capacitance

2.3.1 Passive capacitance

2.3.2 Active capacitance
3 Algorithms
o
3.1 Pattern-based (or image-based) algorithms

4 See also

5 References

6 Reference

7 External links
[edit]Background
The analysis of fingerprints for matching purposes generally requires the comparison of several features of
the print pattern. These include patterns, which are aggregate characteristics of ridges, and minutia points,
which are unique features found within the patterns.[1] It is also necessary to know the structure and
properties of human skin in order to successfully employ some of the imaging technologies.
[edit]Patterns
The three basic patterns of fingerprint ridges are the arch, loop, and whorl:

arch: The ridges enter from one side of the finger, rise in the center forming an arc, and then exit the
other side of the finger.

loop: The ridges enter from one side of a finger, form a curve, and then exit on that same side.

whorl: Ridges form circularly around a central point on the finger.
Scientists have found that family members often share the same general fingerprint patterns, leading to the
belief that these patterns are inherited.[2]
The whorl pattern.
The arch pattern.
The loop pattern.
[edit]Minutia
features
The major Minutia features of fingerprint ridges are: ridge ending, bifurcation, and short ridge (or dot). The
ridge ending is the point at which a ridge terminates. Bifurcations are points at which a single ridge splits
into two ridges. Short ridges (or dots) are ridges which are significantly shorter than the average ridge
length on the fingerprint. Minutiae and patterns are very important in the analysis of fingerprints since no
two fingers have been shown to be identical.[3]
Ridge ending.
Bifurcation.
[edit]Fingerprint
Short Ridge (Dot).
sensors
A fingerprint sensor is an electronic device used to capture a digital image of the fingerprint pattern. The
captured image is called a live scan. This live scan is digitally processed to create a biometric template (a
collection of extracted features) which is stored and used for matching. This is an overview of some of the
more commonly used fingerprint sensor technologies.
[edit]Optical
Optical fingerprint imaging involves capturing a digital image of the print using visible light. This type of
sensor is, in essence, a specialized digital camera. The top layer of the sensor, where the finger is placed,
is known as the touch surface. Beneath this layer is a light-emitting phosphor layer which illuminates the
surface of the finger. The light reflected from the finger passes through the phosphor layer to an array
of solid state pixels (a charge-coupled device) which captures a visual image of the fingerprint. A scratched
or dirty touch surface can cause a bad image of the fingerprint. A disadvantage of this type of sensor is the
fact that the imaging capabilities are affected by the quality of skin on the finger. For instance, a dirty or
marked finger is difficult to image properly. Also, it is possible for an individual to erode the outer layer of
skin on the fingertips to the point where the fingerprint is no longer visible. It can also be easily fooled by an
image of a fingerprint if not coupled with a "live finger" detector. However, unlike capacitive sensors, this
sensor technology is not susceptible to electrostatic discharge damage.
[4]
Fingerprints can be read from a distance.[1]
[edit]Ultrasonic
Ultrasonic sensors make use of the principles of medical ultrasonography in order to create visual images
of the fingerprint. Unlike optical imaging, ultrasonic sensors use very high frequency sound waves to
penetrate the epidermal layer of skin. The sound waves are generated using piezoelectric transducers and
reflected energy is also measured using piezoelectric materials. Since the dermal skin layer exhibits the
same characteristic pattern of the fingerprint, the reflected wave measurements can be used to form an
image of the fingerprint. This eliminates the need for clean, undamaged epidermal skin and a clean sensing
surface.[5]
[edit]Capacitance
Capacitance sensors utilize the principles associated with capacitance in order to form fingerprint images.
In this method of imaging, the sensor array pixels each act as one plate of a parallel-plate capacitor, the
dermal layer (which is electrically conductive) acts as the other plate, and the non-conductive epidermal
layer acts as a dielectric.
[edit]Passive capacitance
A passive capacitance sensor uses the principle outlined above to form an image of the fingerprint patterns
on the dermal layer of skin. Each sensor pixel is used to measure the capacitance at that point of the array.
The capacitance varies between the ridges and valleys of the fingerprint due to the fact that the volume
between the dermal layer and sensing element in valleys contains an air gap. The dielectric constant of the
epidermis and the area of the sensing element are known values. The measured capacitance values are
then used to distinguish between fingerprint ridges and valleys.[6]
[edit]Active capacitance
Active capacitance sensors use a charging cycle to apply a voltage to the skin before measurement takes
place. The application of voltage charges the effective capacitor. The electric field between the finger and
sensor follows the pattern of the ridges in the dermal skin layer. On the discharge cycle, the voltage across
the dermal layer and sensing element is compared against a reference voltage in order to calculate the
capacitance. The distance values are then calculated mathematically, and used to form an image of the
fingerprint.[7] Active capacitance sensors measure the ridge patterns of the dermal layer like the ultrasonic
method. Again, this eliminates the need for clean, undamaged epidermal skin and a clean sensing
surface.[7]
[edit]Algorithms
Matching algorithms are used to compare previously stored templates of fingerprints against candidate
fingerprints for authentication purposes. In order to do this either the original image must be directly
compared with the candidate image or certain features must be compared.[8]
[edit]Pattern-based
(or image-based) algorithms
Pattern based algorithms compare the basic fingerprint patterns (arch, whorl, and loop) between a
previously stored template and a candidate fingerprint. This requires that the images be aligned in the
same orientation. To do this, the algorithm finds a central point in the fingerprint image and centers on that.
In a pattern-based algorithm, the template contains the type, size, and orientation of patterns within the
aligned fingerprint image. The candidate fingerprint image is graphically compared with the template to
determine the degree to which they match.[9]
[edit]See

Fingerprint Verification Competition

Online Fingerprint Identification SDK, Saurabh

Biometrics

Authentication

Fingerprint

Minutiae

Feature extraction

Skin

Heredity

Medical ultrasonography

Piezoelectricity

Biometric technology in access control

Finger Vein recognition

Iris recognition
also
Synchronous dynamic random-access memory
From Wikipedia, the free encyclopedia
Synchronous dynamic random access memory (SDRAM) is dynamic random access memory (DRAM)
that is synchronized with the system bus. Classic DRAM has an asynchronous interface, which means that
it responds as quickly as possible to changes in control inputs. SDRAM has a synchronous interface,
meaning that it waits for a clock signal before responding to control inputs and is therefore synchronized
with the computer's system bus. The clock is used to drive an internal finite state machine that pipelines
incoming commands. The data storage area is divided into several banks, allowing the chip to work on
several memory access commands at a time, interleaved among the separate banks. This allows higher
data access rates than an asynchronous DRAM.
Pipelining means that the chip can accept a new command before it has finished processing the previous
one. In a pipelined write, the write command can be immediately followed by another command, without
waiting for the data to be written to the memory array. In a pipelined read, the requested data appears after
a fixed number of clock cycles after the read command (latency), clock cycles during which additional
commands can be sent. (This delay is called the latency and is an important performance parameter to
consider when purchasing SDRAM for a computer.)
SDRAM is widely used in computers; from the original SDRAM, further generations of DDR (or DDR1) and
then DDR2 and DDR3 have entered the mass market, with DDR4 currently being designed and anticipated
to be available in 2013.
Contents
[hide]

1 SDRAM history

2 SDRAM timing

3 SDR SDRAM
o
3.1 SDRAM control signals

3.1.1 Command signals

3.1.2 Bank Selection (BAn)

3.1.3 Addressing (A10/An)

3.1.4 Commands
o
3.2 SDRAM construction and operation
o
3.3 Command interactions



3.3.1 Interrupting a read burst
o
3.4 SDRAM burst ordering
o
3.5 SDRAM mode register
o
3.6 Auto refresh
o
3.7 Low power modes
4 Generations of SDRAM
o
4.1 SDR SDRAM (Single Data Rate synchronous DRAM)
o
4.2 DDR(1) SDRAM
o
4.3 DDR2 SDRAM
o
4.4 DDR3 SDRAM
o
4.5 DDR4 SDRAM
o
4.6 Feature map
5 Failed successors
o
5.1 Rambus DRAM (RDRAM)
o
5.2 Synchronous-Link DRAM (SLDRAM)
o
5.3 Virtual Channel Memory (VCM) SDRAM

6 See also

7 References
[edit]SDRAM
history
Eight SDRAM ICs on a PC100 DIMMpackage.
Although the concept of synchronous DRAM has been known since at least the 1970s and was used with
early Intel processors, it was only in 1993 that SDRAM began its path to universal acceptance in the
electronics industry. In 1993, Samsung introduced its KM48SL2000 synchronous DRAM, and by 2000,
SDRAM had replaced virtually all other types of DRAM in modern computers, because of its greater
performance.
SDRAM latency is not inherently lower (faster) than asynchronous DRAM. Indeed, early SDRAM was
somewhat slower than contemporaneous burst EDO DRAM due to the additional logic. The benefits of
SDRAM's internal buffering come from its ability to interleave operations to multiple banks of memory,
thereby increasing effective bandwidth.
Today, virtually all SDRAM is manufactured in compliance with standards established by JEDEC, an
electronics industry association that adopts open standards to facilitate interoperability of electronic
components. JEDEC formally adopted its first SDRAM standard in 1993 and subsequently adopted other
SDRAM standards, including those for DDR, DDR2 and DDR3 SDRAM.
SDRAM is also available in registered varieties, for systems that require greater scalability such
as servers and workstations.
As of 2007, 168-pin SDRAM DIMMs are not used in new PC systems, and 184-pin DDR memory has been
mostly superseded. DDR2 SDRAM is the most common type used with new PCs, and DDR3 motherboards
and memory are widely available, and less expensive than still-popular DDR2 products.
Today, the world's larFlash memory is an electronic (i.e. no moving parts) non-volatile computer
storage device that can be electrically erased and reprogrammed.
Flash memory was developed from EEPROM (electrically erasable programmable read-only
memory). There are two main types of flash memory, which are named after
the NAND and NOR logic gates. The internal characteristics of the individual flash memory cells
exhibit characteristics similar to those of the corresponding gates.
Whereas EPROMs had to be completely erased before being rewritten, NAND type flash memory
may be written and read in blocks (or pages) which are generally much smaller than the entire device.
The NOR type allows a single machine word (byte) to be written or read independently.
The NAND type is primarily used in main memory memory cards, USB flash drives, solid-state drives,
and similar products, for general storage and transfer of data. The NOR type, which allows true
random access and therefore direct code execution, is used as a replacement for the
older EPROMand as an alternative to certain kinds of ROM applications. However, NOR flash
memory may emulate ROM primarily at the machine code level; many digital designs need ROM
(or PLA) structures for other uses, often at significantly higher speeds than (economical) flash
memory may achieve. NAND or NOR flash memory is also often used to store configuration data in
numerous digital products, a task previously made possible by EEPROMs or battery-powered static
RAM.
Example applications of both types of flash memory include personal computers, PDAs, digital audio
players, digital cameras, mobile phones, synthesizers, video games, scientific
instrumentation, industrial robotics, medical electronics, and so on. In addition to being non-volatile,
flash memory offers fast read access times, as fast as dynamic RAM, although not as fast as static
RAM or ROM. Its mechanical shock resistance helps explain its popularity over hard disks in portable
devices; as does its high durability, being able to withstand high pressure, temperature, immersion in
water, etc.[1]
Although flash memory is technically a type of EEPROM, the term "EEPROM" is generally used to
refer specifically to non-flash EEPROM which is erasable in small blocks, typically bytes. Because
erase cycles are slow, the large block sizes used in flash memory erasing give it a significant speed
advantage over old-style EEPROM when writing large amounts of data. Flash memory now costs far
less than byte-programmable EEPROM and has become the dominant memory type wherever a
significant amount of non-volatile, solid state storage is needed.
gest manufacturers of SDRAM include: Samsung Electronics, Panasonic, Micron Technology, and Hynix.
[edit]SDRAM
timing
Flash memory is an electronic (i.e. no moving parts) non-volatile computer storage device that can
be electrically erased and reprogrammed.
Flash memory was developed from EEPROM (electrically erasable programmable read-only
memory). There are two main types of flash memory, which are named after
the NAND and NOR logic gates. The internal characteristics of the individual flash memory cells
exhibit characteristics similar to those of the corresponding gates.
Whereas EPROMs had to be completely erased before being rewritten, NAND type flash memory
may be written and read in blocks (or pages) which are generally much smaller than the entire device.
The NOR type allows a single machine word (byte) to be written or read independently.
The NAND type is primarily used in main memory memory cards, USB flash drives, solid-state drives,
and similar products, for general storage and transfer of data. The NOR type, which allows true
random access and therefore direct code execution, is used as a replacement for the
older EPROMand as an alternative to certain kinds of ROM applications. However, NOR flash
memory may emulate ROM primarily at the machine code level; many digital designs need ROM
(or PLA) structures for other uses, often at significantly higher speeds than (economical) flash
memory may achieve. NAND or NOR flash memory is also often used to store configuration data in
numerous digital products, a task previously made possible by EEPROMs or battery-powered static
RAM.
Example applications of both types of flash memory include personal computers, PDAs, digital audio
players, digital cameras, mobile phones, synthesizers, video games, scientific
instrumentation, industrial robotics, medical electronics, and so on. In addition to being non-volatile,
flash memory offers fast read access times, as fast as dynamic RAM, although not as fast as static
RAM or ROM. Its mechanical shock resistance helps explain its popularity over hard disks in portable
devices; as does its high durability, being able to withstand high pressure, temperature, immersion in
water, etc.[1]
Although flash memory is technically a type of EEPROM, the term "EEPROM" is generally used to
refer specifically to non-flash EEPROM which is erasable in small blocks, typically bytes. Because
erase cycles are slow, the large block sizes used in flash memory erasing give it a significant speed
advantage over old-style EEPROM when writing large amounts of data. Flash memory now costs far
less than byte-programmable EEPROM and has become the dominant memory type wherever a
significant amount of non-volatile, solid state storage is needed.
PHY is an abbreviation for the physical layer of the OSI model.
An instantiation of PHY connects a link layer device (often called a Media Access Control, or MAC
address) to a physical medium such as an optical fiber or copper cable. A PHY device typically
includes a Physical Coding Sublayer (PCS) and a Physical Medium Dependent (PMD) layer. The
PCS encodes and decodes the data that is transmitted and received. The purpose of the encoding is
to make it easier for the receiver to recover the signal.
[edit]Example
uses

Wireless LAN or Wi-Fi: The PHY portion consists of the RF, mixed-signal and analog portions,
that are often called transceivers, and the digital baseband portion that use digital signal
processor (DSP) and communication algorithm processing, including channel codes. It is
common that these PHY portions are integrated with the media access control (MAC) layer
inSystem-on-a-chip (SOC) implementations. Other similar wireless applications
are 3G/4G/LTE, WiMAX, UWB, etc.

Ethernet: A PHY chip (PHYceiver) is commonly found on Ethernet devices. Its purpose is
physical, analog signal access to the link. It is usually used in conjunction with an Media
Independent Interface (MII) chip or interfaced to a microcontroller that takes care of the higher
layer functions.

Universal Serial Bus (USB): A PHY chip is integrated into most USB controllers in hosts
or embedded systems and provides the bridge between the digital and modulated parts of the
interface.

IrDA: The Infrared Data Associations (IrDA) specification includes an IrPHY specification for the
physical layer of the data transport.

Serial ATA (SATA): Serial ATA controllers like the VIA Technologies VT6421 use a PHY.

SDRAM chip interfaces

Flash memory chip interfaces
Charge-coupled device
From Wikipedia, the free encyclopedia
A specially developed CCD used for ultraviolet imaging in a wire bonded package
A charge-coupled device (CCD) is a device for the movement of electrical charge, usually from within the
device to an area where the charge can be manipulated, for example conversion into a digital value. This is
achieved by "shifting" the signals between stages within the device one at a time. CCDs move charge
between capacitive bins in the device, with the shift allowing for the transfer of charge between bins.
The CCD is a major piece of technology in digital imaging. In a CCD image sensor, pixels are represented
by p-doped MOS capacitors. These capacitors are biased above the threshold for inversion when image
acquisition begins, allowing the conversion of incoming photonsinto electron charges at the semiconductoroxide interface; the CCD is then used to read out these charges. Although CCDs are not the only
technology to allow for light detection, CCD image sensors are widely used in professional, medical, and
scientific applications where high-quality image data is required. In applications where a somewhat lower
quality can be tolerated, such as webcams, cheaper active pixel sensors (CMOS) are generally used.
Active Directory
From Wikipedia, the free encyclopedia
Active Directory (AD) is a directory service created by Microsoft for Windows domain networks. It is
included in most Windows Server operating systems.
Active Directory provides a central location for network administration and security. Server computers that
run Active Directory are called domain controllers. An AD domain controller authenticatesand authorizes all
users and computers in a Windows domain type network—assigning and enforcing security policies for all
computers and installing or updating software. For example, when a user logs into a computer that is part
of a Windows domain, Active Directory checks the submitted password and determines whether the user is
a system administrator or normal user.[1]
Active Directory makes use of Lightweight Directory Access Protocol (LDAP) versions 2 and
3, Kerberos and DNS.
The PCI Bus
The PCI bus (Peripheral Component Interconnect) was developed by Intel on 22 June 1992. Contrary
to the VLB bus, it is not so much a traditional local bus but rather an intermediate bus located
between theprocessor bus (NorthBridge) and the I/O bus (SouthBridge).
PCI Connectors
At least 3 or 4 PCI connectors are generally present on motherboards and can generally be
recognised by their standardized white color.
The PCI interface exists in 32 bits with a 124-pin connector, or in 64 bits with a 188-pin connector.
There are also two signalling voltage levels:

3.3V, for laptop computers

5V, for desktop computers
The signalling voltage does not equal the voltage of the motherboard power supply but rather the
voltage threshold for the digital encryption of data.
There are 2 types of 32-bit connectors:

32-bit PCI connector, 5V:

32-bit PCI connector, 3.3V:
The 64-bit PCI connectors offer additional pins and can accommodate 32-bit PCI cards. There are 2
types of 64-bit connectors:

64-bit PCI connector, 5V:

64-bit PCI connector, 3.3V:
Interoperability
Generally, it is not possible to make a mistake when plugging a PCI card into a PCI slot. If the card
plugs in correctly, it is compatible. Otherwise, there are foolproof devices to keep you from installing it.
There are expansion boards that have what are called "universal" connectors, i.e. that have two
types of foolproof devices (two notches). These expansion cards can detect signalling voltage and
adapt to it, and can therefore can be inserted independantly in 3.3V or 5V slots.