Tuesday, August 7, 2007

What is WI-FI(Wireless Fidelity)Wi-Fi was originally a brand licensed by the Wi-Fi Alliance to describe the embedded technology of wireless local area networks (WLAN) based on the IEEE 802.11 standard. As of 2007, common use of the term Wi-Fi has broadened to describe the generic wireless interface of mobile computing devices, such as laptops in LANs. The term Wi-Fi was chosen as a play on the term "Hi-Fi", and is often thought to be an abbreviation for wireless fidelity, though the Wi-Fi Alliance no longer recognizes such. Wi-Fi and the Wi-Fi CERTIFIED logo are registered trademarks of the Wi-Fi Alliance, the trade organization that tests and certifies equipment compliance with the 802.11 standards.Common uses for Wi-Fi include Internet and VoIP phone access, gaming, and network connectivity for consumer electronics such as televisions, DVD players, and digital cameras. In spite of media reports about possible health risks from Wi-Fi, scientific studies have failed to show a causal effect.

Different Network Topology· ring · mesh · star · fully connected · line · tree · busUTP- Unshielded twisted pair is the most common kind of copper telephone wiring. wire uses metallic conductors, providing a path for current flow that represents information.As the name implies, UTP wiring doesn’t include shielding found in other forms oftwisted-pair wires. The wire is twisted in pairs to minimize the electromagnetic interference resulting from adjacent wire pairs and external noise sources. A greater number of twists-per foot increase noise immunity.Maximum distance: 328 ft. (100 m) Maximum speed: Unshielded (UTP) 10Base-T TWISTED PAIR=10 Mbps Unshielded (UTP) 100Base-T TWISTED PAIR=100MbpsAdvantages of UTP · inexpensive to purchase · easy to install· currently the industry standard for wiring LANs. It is a thin, flexible cable that is easy to string between walls. Most modern buildings come with CAT 5 UTP already wired into the wall outlets or at least run between the floors. Because UTP is small, it does not quickly fill up wiring ducts. UTP costs less per foot than any other type of LAN cable. Disadvantages of UTPUTP cables are not shielded. This lack of shielding results in a high degree of flexibility as well as rugged durability. Twisted pair’s susceptibility to the electromagnetic interference greatly depends on the pair twisting schemes (usually patented by the manufacturers) staying intact during the installation. As a result, twisted pair cables usually have stringent requirements for maximum pulling tension as well as minimum bend radius. This relative fragility of twisted pair cables makes the installation practices an important part of ensuring the cable’s performance
STP- Shielded twisted pair is a special kind of copper telephone wiring used in some business installations. An outer covering or shield is added to the ordinary twisted pair telephone wires; the shield functions as a ground. Maximum distance:328 ft.(100 m)maximum speed: 16 - 155 MbpsAdvantages of STP· includes metal shielding over each individual pair of copper wires· This type of shielding protects cable from external EMI (electromagnetic interferences).· are part of an IEEE standard that is well supported by the various vendors allowing for the mixing of vendor equipment in the field.· not limited to just ring topology· also be used in a star topology to guard against cabling mistakes that can result in a loopDisadvantages of STP· The extra shielding can make the cables quite bulky.· very complex to understand and difficult to configure· Parameters may need to be "tuned" in the field in order to yield acceptable recovery times· has a very slow recovery time and represents the "old" standard· recovery time may be unacceptable.FireWire - is Apple Inc.'s brand name for the IEEE 1394 interface (although the 1394 standard also defines a backplane interface). It is also known as I. Link (Sony’s name). It is a personal computer (and digital audio/digital video) serial bus interface standard, offering high-speed communications and isochronous real-time data services. FireWire has replaced Parallel SCSI in many applications, due to lower implementation costs and a simplified, more adaptable cabling system. IEEE 1394 has been adopted as the High Definition Audio-Video Network Alliance (HANA) standard connection interface for A/V (audio/visual) component communication and control[1]. FireWire is also available in wireless, fibre optic and coaxial versions using the isochronous protocols. Wireless FireWire is being integrated into the WiMedia Alliance's WiMedia Ultra-Wideband (UWB) standard.Maximum speed: 100, 200 or 400MbpsMaximum distance: 237 feet.



Advantages of firewire· can connect almost all computer peripherals such as printers, scanners, modems, keyboards, displays (monitors), hard drives and CD-ROM drives.· supports the connection of digital cameras, digital camcorders and televisions, along with all other digital consumer audio and video equipment.· FireWire is an established protocol, it has been around for some time and there are many devices available which use it. Mainly found on the Apple platform, it is easy to set up and use, and it has a very good history of trouble free use. Unlike USB 2.0, FireWire devices can be chained together, allowing well many firewire products to run from a single FireWire connection, USB 2.0 on the other hand still uses the old master/slave methodology, meaning they cannot be chained together - therefore you need a USB hub if you wish to have extra devices.Disadvantages of firewire·most PCs don't come from the factory with Firewire ports and that many devices on the market today are not being built with Firewire capability.·Unavailability, Fewer computers sport FireWire than those with USB, and only a handful of FireWire interfaces are even on the market. The ones that exist are mid- to high-pricedOptical cable- functions as a "light guide," guiding the light introduced at one end of the cable through to the other end. The light source can either be a light-emitting diode (LED)) or a laser.The light source is pulsed on and off, and a light-sensitive receiver on the other end of the cable converts the pulses back into the digital ones and zeros of the original signal.• SPEED: Fiber optic networks operate at high speeds - up into the gigabits• DISTANCE: Signals can be transmitted further without needing to be "refreshed" or strengthenedAdvantages of Optical CableVery robust, this connector style is based on tried and true technology, and can withstand the greatest environmental and mechanical stress when compared to the other connector technologies.This style of connector accepts the widest assortment of cable jacket diameters. Most connectors of this group have versions to fit onto 900um buffered fiber, and up to 3.0mm jacketed fiber.• Versions are. available that hold from 1 to 24 fibers in a single connector.
Installation Time: There is an initial setup time for the field technician who must prepare a workstation with polishing equipment and an epoxy-curing oven. The termination time for one connector is about 25 minutes due to the time needed to heat cure the epoxy. Average time per connector in a large batch can be as low as 5 or 6 minutes. Faster curing epoxies such as anaerobic epoxy can reduce the installation time, but fast cure epoxies are not suitable for all connectors.Skill Level: These connectors, while not difficult to install, do require the most supervised skills training, especially for polishing. They are best suited for the high-volume installer or assembly house with a trained and stable work force.Costs: Least expensive connectors to purchase, in many cases being 30 to 50 percent cheaper than other termination style connectors. However, factor in the cost of epoxy curing and ferrule polishing equipment, and their associated consumables.Disadvantage of optical cablePrimary disadvantage of optical cable is that is largely restricted to point-to-point communications.TN104 - UTP Wiring104.1 Standard EIA/TIA T568A 104.2 Standard EIA/TIA T568B 104.3 USOC (Universal Service Order Code) 104.4 Pin Numbering 104.5 Cable Pinouts 104.6 Category Specifications 104.7 Cables Making Tools 104.1 Standard EIA/TIA T568APin Wire Color=== ==========/--T3 1 White/GreenPair3 \--R3 2 Green/----------T2 3 White/Orange/ /-R1 4 Bluepair2 \ pair1 \-T1 5 White/Blue\----------R2 6 Orange/--T4 7 White/Brownpair4 \--R4 8 Brown104.2 Standard EIA/TIA T568B(also called AT&T specification, previously called 258A)/--T2 1 White/Orangepair2 \--R2 2 Orange/----------T3 3 White/Green/ /-R1 4 Bluepair3 \ pair1 \-T1 5 White/Blue\----------R3 6 Green/--T4 7 White/Brownpair4 \--R4 8 Brown104.3 USOC (Universal Service Order Code)8-pins 6-pins /-------------T4 1 White/Brown/ /---------T3 2 1 White/Green/ / /-----T2 3 2 White/Orange/ / / /-R1 4 3 Bluepr4\ pr3\ pr2\ pr1\-T1 5 4 White/Blue\ \ \-----R2 6 5 Orange\ \---------R3 7 6 Green\-------------R4 8 Brown104.4 Pin NumberingThe EIA/TIA specifies an RJ-45 (ISO 8877) connector for UnshieldedTwisted Pair (UTP) cable.Plug Jack(Looking at connector (Looking at cavityend with the cable in the wall)running away from you)---------- / ---------- 87654321 12345678 __ __/ /_ /_____ /___104.5 Cable PinoutsWith reference to T568B above:ATM 155Mbps uses pairs 2 and 4 (pins 1-2, 7-8)Ethernet 10Base-T uses pairs 2 and 3 (pins 1-2, 3-6)Ethernet 100Base-T4 uses pairs 2 and 3 (4T+) (pins 1-2, 3-6)Ethernet 100Base-T8 uses pairs 1,2,3 and 4 (pins 4-5, 1-2, 3-6, 7-8)Token-Ring uses pairs 1 and 3 (pins 4-5, 3-6)TP-PMD uses pairs 2 and 4 (pins 1-2, 7-8)100VG-AnyLAN uses pairs 1,2,3 and 4 (pins 4-5, 1-2, 3-6, 7-8)Ethernet 10Base-T Straight Thru patch cord (T568B colors);RJ45 Plug RJ45 Plug========= =========/--T2 1 ... White/Orange .... 1 TxData +pair2 \--R2 2 ... Orange .......... 2 TxData -/----------T3 3 ... White/Green ..... 3 RecvData +/ R1 4 Blue 4\ pair3 T1 5 White/Blue 5\----------R3 6 ... Green ........... 6 RecvData -T4 7 White/Brown 7R4 8 Brown 8Ethernet 10Base-T Crossover patch cord;RJ45 Plug 1 Tx+ -------------- Rx+ 3 RJ45 Plug2 Tx- -------------- Rx- 63 Rx+ -------------- Tx+ 16 Rx- -------------- Tx- 2Ethernet 10Base-T to USOC Crossover patch cord;RJ45 8-pin Plug 1 ---White/Orange--- 2 USOC 6-pin Plug2 ------Orange------ 53 ---White/Green---- 16 ------Green------- 6Stranded Patch CablesThe color code used in stranded patch cables is different fromsolid-conductor cables. For NorTel Digital Patch Cable (DPC),the coding is;Pair 1: Green & RedPair 2: Yellow & BlackPair 3: Blue & OrangePair 4: Brown & Gray104.6 Category SpecificationsEIA/TIA Category Specification provide for the following cabletransmission speeds with specifications:Category 1 = No performance criteriaCategory 2 = Rated to 1 MHz (used for telephone wiring)Category 3 = Rated to 16 MHz (used for Ethernet 10Base-T)Category 4 = Rated to 20 MHz (used for Token-Ring, 10Base-T)Category 5 = Rated to 100 MHz (used for 100Base-T, 10Base-T)104.7 Cables Making ToolsIt is imperative to use a quality connector, tool, and cableFurther, the connectors and tool must be designed for each otherdo not mix one brand of connector with another brand of tool.Recommended tool:AMP Terminating tool for modular plugs: pn 231652Complete set of tool, dies, and case: pn 1-231666-4Dies for various size plugs:AMP PN color description---------- ------ --------------------------------------1-853400-0 white 8 position CAT5 (RJ-45)853400-1 black 8 position line (RJ-45)853400-8 blue 6 position (RJ-11)853400-3 green 4 position (handset)Plugs:AMP PN conductor cable conductor type---------- -------- ---------- --------- -------5-641334-2 4 flat oval stranded handset5-641335-2 4 flat oval stranded line (RJ-11)5-641337-2 6 flat oval stranded line (RJ-11)5-554739-2 8 flat oval stranded line (RJ-45)5-558530-2 8 round stranded CAT5 certified5-569278-2 8 round solid CAT5 certified

Thursday, July 19, 2007

LAN;WAN

Local-area network

A computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. Most LANs connect workstations and personal computers. Each node (individual computer) in a LAN has its own CPU with which it executes programs, but it also is able to access data and devices anywhere on the LAN.

The following characteristics differentiate one LAN from another:

Topology: The geometric arrangement of devices on the network. For example, devices can be arranged in a ring or in a straight line.
Protocols: The rules and encoding specifications for sending data. The protocols also determine whether the network uses a peer-to-peer or client/server architecture.
Media: Devices can be connected by twisted-pair wire, coaxial cables, or fiber optic cables. Some networks do without connecting media altogether, communicating instead via radio waves.
LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line; but the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN.
A Wide Area Network (WAN) is a network that spans a large geographical area, the most common example being the Internet. A WAN is contrasted to smaller local area networks (LANs) and metropolitan area networks (MANs). LANs are home or office networks, while a MAN might encompass a campus or service residents of a city, such as in a citywide wireless or WiFi network.
The Internet is a public WAN, but there are many ways to create a business model or private WAN. A private WAN is essentially two or more LANs connected to each other. For example, a company with offices in
Los Angeles, Texas and New York might have a LAN setup at each office. Through leased telephone lines, all three LANs can communicate with each other, forming a WAN.
Routers are used to direct communications between LANs communicating on a WAN. The router, installed on the leased line, reads the "envelopes" or headers on each packet of data that passes through the WAN, sending it to the proper LAN. When the packet arrives at the LAN, a device called a switch sends the data packet on to the correct machine. Hence, the WAN acts like an interface between LANs for long-distance communication. A WAN that runs on a leased line is a private WAN, as there is no public traffic on the line.

Tuesday, July 10, 2007



MODEL AL2616Wd PART # ET.G16WP.001UPC 099802724795WE ARE AN APPROVED ACER AUTHORIZED RESELLER! WE SHIP WORLDWIDE!
Acer AL2616Wd Flat panel display - TFT - 26" - widescreen - 1920 x 1200 - 500 cd/m2 - 800:1 - 5 ms - DVI-D, VGA - silver
Manufacturer:
Acer
Part #:
ET.G16WP.001
Since its inception, Acer has evolved from a manufacturing powerhouse to a globally recognized computer brand, marketing world-class IT products and services. Acer's complete range of IT products is designed to enhance work efficiency and quality of life, while granting an easy, hassle-free user experience.

Main Specifications
Product Description
Acer AL2616Wd - flat panel display - TFT - 26"
Device Type
Flat panel display / TFT active matrix
Color
Silver
Localization
Canada, United States
Diagonal Size
26" - widescreen
Max Resolution
1920 x 1200
Response Time
5 ms
Image Brightness
500 cd/m2
Image Contrast Ratio
800:1
Digital Video Standard
Digital Visual Interface (DVI)
Signal Input
DVI-D, VGA
Compliant Standards
PC 99
Manufacturer Warranty
3 years warranty
General
Display Type
Flat panel display / TFT active matrix
Enclosure Color
Silver
Localization
Canada, United States
Display
Diagonal Size
26" - widescreen
Max Resolution
1920 x 1200
Response Time
5 ms
Signal Input
DVI-D, VGA
Image
Image Brightness
500 cd/m2
Image Contrast Ratio
800:1
Image Max H-View Angle
178
Image Max V-View Angle
178
Video Input
Analog Video Signal
RGB
Digital Video Standard
Digital Visual Interface (DVI)
Expansion / Connectivity
Interfaces
1 x VGA - 15 pin HD D-Sub (HD-15) 1 x DVI-D - 24 pin digital DVI
Miscellaneous
Flat Panel Mount Interface
Yes
Features
Security lock slot (cable lock sold separately)
Compliant Standards
PC 99
Power
Form Factor
Internal
Manufacturer Warranty
Service & Support
3 years warranty
Service & Support Details
Limited warranty - 3 years INTERNATIONAL BUYERS, WE NEED YOUR TELEPHONE NUMBER FOR THE CUSTOMS FORMS.THANK YOU FOR YOUR BUSINESS!