Technology of Electronics,Telecomunication, IT

ABOUT SRI LANKA

noreply@blogger.com (Nimesha) — Thu, 23 Oct 2025 11:32:00 -0700

Sri Lanka is a tropical island nation in the Indian Ocean, known for its golden beaches, lush rainforests, rolling tea plantations, ancient cities, and diverse wildlife. Visitors can enjoy vibrant culture, delicious cuisine, and friendly hospitality while exploring world heritage sites like Sigiriya Rock Fortress, the sacred city of Kandy, and beautiful national parks rich in elephants and leopards. It’s an excellent travel destination for those seeking a blend of adventure and relaxation in stunning natural settings.

Introduction to satellite communications

noreply@blogger.com (Nimesha) — Fri, 30 Jul 2010 00:24:00 -0700

HISTORY OF SATELLITE COMMUNICATIONS

The first artificial satellite was placed in orbit by the Russians in 1957. That satellite, called Sputnik, signaled the beginning of an era.

The United States, who was behind the Russians, made an all-out effort to catch up, and launched Score in 1958. That was the first satellite with the primary purpose of communications.

The first regular satellite communications service was used by the Navy in 1960. The moon was used to bounce teletypewriter signals between Hawaii and Washington, D.C. During the early 1960s, the Navy used the moon as a medium for passing messages between ships at sea and shore stations. This method of communications proved reliable when other methods failed.

Military satellite communications technology was at a low level until 1965. At that time high quality voice transmissions were conducted between a satellite and two earth stations. That was the stepping stone to the Initial Defense Communications Satellite Program (IDCSP), which will be covered later in this chapter.

Experience with satellite communications has demonstrated that satellite systems can satisfy many military requirements. They are reliable, survivable, secure, and a cost effective method of telecommunications. You can easily see that satellites are the ideal, if not often the only, solution to problems of communicating with highly mobile forces. Satellites, if properly used, provide much needed options to large, fixed-ground installations.

For the past fifty years, the Navy has used high-frequency (hf) transmissions as the principal method of sending messages. In the 1970s, the hf spectrum was overcrowded and "free" frequencies were at a premium. Hf jamming and electronic countermeasures (ECM) techniques became highly sophisticated during that period. As a result the need for new and advanced long-range transmission methods became apparent.

Communications via satellite is a natural outgrowth of modern technology and of the continuing demand for greater capacity and higher quality in communications.

In the past, the various military branches have had the resources to support their communications needs. Predicted usage indicates that large-scale improvements will have to be made to satisfy future needs of the Department of Defense. These needs will require greater capacity for long-haul communications to previously inaccessible areas. Satellite communications has the most promise for satisfying these future requirements.

FUNDAMENTAL SATELLITE COMMUNICATIONS SYSTEM

A satellite communications system uses satellites to relay radio transmissions between earth terminals. The two types of communications satellites you will study are ACTIVE and PASSIVE. A passive satellite only reflects received radio signals back to earth. An active satellite acts as a REPEATER; it amplifies signals received and then retransmits them back to earth. This increases signal strength at the receiving terminal to a higher level than would be available from a passive satellite.

A typical operational link involves an active satellite and two or more earth terminals. One station transmits to the satellite on a frequency called the UP-LINK frequency. The satellite then amplifies the signal, converts it to the DOWN-LINK frequency, and transmits it back to earth. The signal is next picked up by the receiving terminal. Figure 4-1 shows a satellite handling several combinations of links simultaneously.

BidVertiser

noreply@blogger.com (Nimesha) — Mon, 19 Apr 2010 22:23:00 -0700

Electronic Marketing (e-commerce)

noreply@blogger.com (Nimesha) — Sun, 14 Feb 2010 23:09:00 -0800

Earn money with AlertPay

Electronic commerce, commonly known as (electronic marketing) e-commerce or eCommerce, consists of the buying and selling of products or services over electronic systems such as the Internet and other computer networks. The amount of trade conducted electronically has grown extraordinarily with widespread Internet usage. The use of commerce is conducted in this way, spurring and drawing on innovations in electronic funds transfer, supply chain management, Internet marketing, online transaction processing, electronic data interchange (EDI), inventory management systems, and automated data collection systems. Modern electronic commerce typically uses the World Wide Web at least at some point in the transaction's lifecycle, although it can encompass a wider range of technologies such as e-mail as well.
A large percentage of electronic commerce is conducted entirely electronically for virtual items such as access to premium content on a website, but most electronic commerce involves the transportation of physical items in some way. Online retailers are sometimes known as e-tailers and online retail is sometimes known as e-tail. Almost all big retailers have electronic commerce presence on the World Wide Web.
Electronic commerce that is conducted between businesses is referred to as business-to-business or B2B. B2B can be open to all interested parties (e.g. commodity exchange) or limited to specific, pre-qualified participants (private electronic market). Electronic commerce that is conducted between businesses and consumers, on the other hand, is referred to as business-to-consumer or B2C. This is the type of electronic commerce conducted by companies such as Amazon.com.
Electronic commerce is generally considered to be the sales aspect of e-business. It also consists of the exchange of data to facilitate the financing and payment aspects of the business transactions

What is FOREX (Foreign Exchange)?

noreply@blogger.com (Nimesha) — Tue, 9 Jun 2009 01:44:00 -0700

The simple sense of Forex (Forex currency exchange, Foreign Exchange) is simultaneous purchase and sale of the currency or the exchange of one country's currency for the one of another country. The world currencies do not have a fixed exchange rate and are always fluctuating being traded in the currency pairs like Euro/Dollar, Dollar/Yen an others. 85% of daily trades are taken by major currencies trading.

Investments usually deal with 4 major pairs: Euro against US dollar, US dollar against Japanese yen, British pound against US dollar, and US dollar against Swiss franc or EUR/USD, USD/JPY, GBP/USD, and USD/CHF used to sign these pairs accordingly. These major pairs are considered as Forex market's "blue chips". You will not receive any dividends on the currencies. Well known "buy low - sell high" gives the profit for currency trades.

In case you have a forecast that one currency would get higher to another you can exchange the second one for the first one and wait for the profit. If you are lucky to see the trades following your forecast you can make an opposite transaction and to exchange currencies back gaining the profit.

3G mobile and HSDPA for Internet

noreply@blogger.com (Nimesha) — Mon, 23 Mar 2009 02:02:00 -0700

HSDPA

High-Speed Downlink Packet Access (HSDPA) is a 3G (third generation) mobile telephony communications protocol in the High-Speed Packet Access (HSPA) family, which allows networks based on Universal Mobile Telecommunications System (UMTS) to have higher data transfer speeds and capacity. Current HSDPA deployments support down-link speeds of 1.8, 3.6, 7.2 and 14.4 Mbit/s. Further speed increases are available with HSPA+, which provides speeds of up to 42 Mbit/s downlink.

Technology

The High-Speed Downlink Shared Channel (HS-DSCH) lacks two basic features of other W-CDMA channels—variable spreading factor and fast power control. Instead, it delivers the improved downlink performance using adaptive modulation and coding (AMC), fast packet scheduling at the base station, and fast retransmissions from the base station, known as hybrid automatic repeat-request (HARQ).

Marketing as mobile broadband

During 2007, an increasing number of telcoms worldwide began selling HSDPA USB modems as mobile broadband connections. In addition, the popularity of HSDPA landline replacement boxes grew—providing HSDPA for data via Ethernet and WiFi, and ports for connecting traditional landline telephones. Some are marketed with connection speeds of "up to 7.2 Mbit/s",[3] which is only attained under ideal conditions. As a result these services can be slower than expected, especially when in fringe coverage indoors. However, signal strength can be greatly improved by using commercial solutions that can attach 3G external antennas

Protection of Computer fromVirus

noreply@blogger.com (Nimesha) — Sat, 23 Aug 2008 01:17:00 -0700

http://www.f-secure.com/download-purchase/tools.shtml

ANTIVIRUS SOFTWARE LIST

eScan AntiVirus
ArcaVir by arcabit.com
avast!
Avira
AVG Anti-Virus
BitDefender
BullGuard
CA Anti-Virus
Cisco Security Agent
Dr.Web
DriveSentry (antivirus, antispyware and HIPS technologies)
eSafe
Fortinet FortiClient End Point Security
F-PROT
F-Secure
G DATA AntiVirus
IKARUS antivirus
INCA Internet
Kaspersky Anti-Virus
LinuxShield
McAfee VirusScan
Mks vir
NOD32
Norman ASA
Norton AntiVirus
Panda Security
PC Tools AntiVirus
Rising AntiVirus
Sophos Anti-Virus
Trend Micro Internet Security
TrustPort Antivirus -AEC
Vba32 AntiVirus
Virus Chaser
Windows Live OneCare
ZoneAlarm

Intel Microprocessor 805xx product codes

noreply@blogger.com (Nimesha) — Thu, 21 Aug 2008 01:54:00 -0700

List of Intel Microprocessor

Scanners,Photocopy and Laser Printer

noreply@blogger.com (Nimesha) — Mon, 18 Aug 2008 22:24:00 -0700

Scanner

Scanner OperationThe Cyberware 3D Scanners are designed to scan a wide variety of objects in many configurations. The following sections describe how the scanners work and how they are controlled.
Theory of OperationThe scanner operates on the principle that light in a straight line, reflected off an object, can be viewed at a different angle to reveal a profile of the surface. The greater the angle between the light source and the viewing point, the more pronounced the description of the shape; however, the risk of a given surface being in shadow also increases. The scanner uses a plane of laser light which can be distinguished from most ambient light, and has two viewing points positioned at equal angles on both sides of the light source. A beam splitter (one-way mirror) is used to overlay the two images, so that if one side is shadowed, the other will normally contain the data. A system of mirrors inside the scanner enables the optics to be contained in a smaller space than would otherwise be necessary.

Photocopy system

A photocopy system provides a halftone image of a picture composed of continuous tones by producing a plurality of hollow halftone dots corresponding to the continuous tones. Each of the halftone dots comprises an annulus that has a size that corresponds to the density of a tone on the original picture

Laser Printer

Static electricity is the principle behind laser printing which uses a revolving cylinder, a laser beam, fine powder toner, and heat to create images on paper. Black and white lasers (black toner) are relatively inexpensive and common in many homes and small offices. Color lasers are typically found in service bureaus and commercial printers and may be used to produce high-resolution color digital proofs. Adobe PostScript capabilities found in many laser printers make them popular with graphic designers and desktop publishers who often utilize EPS images and PostScript files. Hewlett-Packard's PCL language is another popular command language used by laser printers.See Laser Printing for more details on operation, history, and current

Television Block Diagram

noreply@blogger.com (Nimesha) — Sun, 17 Aug 2008 21:22:00 -0700

What is GSM,CDMA,TDMA

noreply@blogger.com (Nimesha) — Sun, 17 Aug 2008 21:17:00 -0700

TDMA

Short for Time Division Multiple Access, a technology for delivering digital wireless service using time-division multiplexing (TDM). TDMA works by dividing a radio frequency into time slots and then allocating slots to multiple calls. In this way, a single frequency can support multiple, simultaneous data channels. TDMA is used by the GSM digital cellular system.

CDMA

Short for Code-Division Multiple Access, a digital cellular technology that uses spread-spectrum techniques. Unlike competing systems, such as GSM, that use TDMA, CDMA does not assign a specific frequency to each user. Instead, every channel uses the full available spectrum. Individual conversations are encoded with a pseudo-random digital sequence. CDMA consistently provides better capacity for voice and data communications than other commercial mobile technologies, allowing more subscribers to connect at any given time, and it is the common platform on which 3G technologies are built.
CDMA is a military technology first used during World War II by English allies to foil German attempts at jamming transmissions. The allies decided to transmit over several frequencies, instead of one, making it difficult for the Germans to pick up the complete signal. Because Qualcomm created communications chips for CDMA technology, it was privy to the classified information. Once the information became public, Qualcomm claimed patents on the technology and became the first to commercialize.

GSM

GSM (Global System for Mobile communication) is a digital mobile telephony system that is widely used in Europe and other parts of the world. GSM uses a variation of time division multiple access (TDMA) and is the most widely used of the three digital wireless telephony technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1800 MHz frequency band. Mobile services based on GSM technology were first launched in Finland in 1991. Today, more than 690 mobile networks provide GSM services across 213 countries and GSM represents 82.4% of all global mobile connections. According to GSM World, there are now more than 2 billion GSM mobile phone users worldwide. GSM World references China as "the largest single GSM market, with more than 370 million users, followed by Russia with 145 million, India with 83 million and the USA with 78 million users."
Since many GSM network operators have roaming agreements with foreign operators, users can often continue to use their mobile phones when they travel to other countries. SIM cards (Subscriber Identity Module) holding home network access configurations may be switched to those will metered local access, significantly reducing roaming costs while experiencing no reductions in service.

GPRS

noreply@blogger.com (Nimesha) — Mon, 11 Aug 2008 20:41:00 -0700

GPRS

GPRS (General Packet Radio Service) is a non-voice service added to existing TDMA networks, one of the 2.5G technology upgrades. TDMA is the underlying transport mechanism used by GSM networks.

GPRS provides the transmission of IP packets over existing cellular networks.

How does it work?

GPRS is a network overlay to the existing cellular network. It uses the nature of IP transmissions to its advantage. Because IP traffic is made of “packets”, the network does not need to have continuous data transmission. Thus, IP traffic can easily share the channels. A user may be receiving or transmitting data while another one is reading information. The second user does not need to use the channel during this time, and it makes packet networks more efficient than circuit-switched networks (2G), where the channel would be in use, regardless of the user transmitting or not.

Each channel is divided into eight time slots, with a maximum data transmission of 13.4Kbps. One of these time slots is used for control, and normal allocation would reserve two slots for voice traffic as well. Asymmetric traffic (more download than uploads) dictates the distribution of the remaining time slots:

Type Meaning
2+1 two slots for download + 1 for upload
3+1 three slots for download + 1 for upload
4+1 four slots for download + 1 for upload

Also, the GPRS devices have a classification related to their ability to handle GSM voice calls and GPRS connections:

Class Meaning
A devices are capable of simultaneous voice and data transmission
B devices support one type at a time, and switch automatically between data and voice
C devices support one type at a time, and require user intervention to switch between data and voice

In theory the GPRS data rate is 171.2Kbps per channel, but users will experience something lower than this, because of the nature of channel usage explained before.

The maximum rate a user can have using a Type 4+1 device is 53.6Kbps.

The connection to the GPRS network is always on, but the device needs to connect to the data terminal (Pocket PC, notebook, cellular phone). The connection times are of course much lower than dial up. My personal tests show GPRS connection to be ready to use in 7 seconds, while a dial up requires around 35 seconds to be in a ready state.

How to use GPRS

A user can connect to a GPRS enable network in three different ways:

Using a mobile with a microbrowser to access WAP pages A user can connect to the GPRS and browse WAP pages from a GPRS enabled mobile. Of course the impact of reduced content on WML format and using the little phone keypad to type in URLs is tiresome. Examples are mobile phones such as Ericsson T39m and T68i.
Using a handheld with built in GSM/GPRS capabilities Using handhelds with GPRS capabilities a user can connect to the GPRS network. All Internet services will be available, providing the needed ports are not blocked. This includes web, e-mail, newsgroups, VPN, ftp, etc. The connection between the terminal and the GPRS modem can be via infrared, serial cable or bluetooth. Examples are Treo, XDA Pocket PC Phone Edition, and Smartphones.
Using a mobile as a GPRS modem A user can connect a notebook, desktop or handheld to connect to a GPRS enabled mobile, and then connect to the Internet. All Internet services will be available, providing the needed ports are not blocked. This includes web, e-mail, newsgroups, VPN, ftp, etc. The connection between the terminal and the GPRS modem can be via infrared, serial cable or bluetooth. Examples are using a H3970 to link via Bluetooth to a T39m and from there to the Internet.
Using a PCMCIA card as a GPRS modem A PCMCIA card can be used as a GPRS enabled modem, and once inserted a dial up connection can be created. From there the user can connect to the Internet. All Internet services will be available, providing the needed ports are not blocked. This includes web, e-mail, newsgroups, VPN, ftp, etc.

noreply@blogger.com (Nimesha) — Sun, 12 Aug 2007 01:53:00 -0700

Hi Everybody!!!