Precautions from virus attacks

1. A number of general precautions are herewith provided to minimize the possibility of virus infection. 
2. Back up important data frequently and keep them in a safe place other than the computer.
3. Patch the operating system as quickly as possible to block the potential vulnerabilities that malware can exploit and sneak in.
4. Obtain the most recent virus definition to keep the antivirus application up-to-date.
5. Be suspicious of e-mail attachments from unknown sources and scan them first; be cautious when opening e-mail attachments even from known sources, because e-mail attachments are currently a major source of infection and sophisticated viruses can automatically send e-mail messages from other’s address books.
6. Scan all new software before installing and opening, particularly the media that belong to other people. Sometimes even the trial and retail software has viruses.
7. Be extremely vigilant with external sources, such as CDs, Pen drives and Web links.
8. Always keep application’s auto-protect running. Set the application default to auto-protection upon the launch of system.
9. Now-a-days the USB ports are the major reasons for spreading viruses. So, always try to explore any device than directly opening it Scan the pen drives before opening it.

Prevention from Viruses in OS:

Additionally, many recent significant outbreaks of virus stem from Operating System (OS) vulnerabilities. Vulnerabilities can exist in large and complex software systems as well as human carelessness and sabotage.
Virus writers have demonstrated a growing tendency to exploit system vulnerabilities to propagate their malicious code. Operating systems consist of various and complex yet vulnerable software components that play a crucial role in the achievement of overall system security, since many protection mechanisms and facilities, such as authentication and access control, are provided by the operating system.
Vulnerabilities and methods for closing them vary greatly from one operating system to another. Therefore, it is of vital importance to screen these following items in the following two famous usable OS.

Microsoft Windows:

• Internet Information Services (IIS)
• Microsoft SQL Server (MSSQL)
• Windows Authentication
• Internet Explorer (IE)
• Windows Remote Access Services
• Microsoft Data Access Components (MDAC)
• Windows Scripting Host (WSH)
• Microsoft Office Suite (Word and Excel)
• Microsoft Outlook and Outlook Express
• Windows Peer to Peer File Sharing (P2P)
• Simple Network Management Protocol (SNMP)
• Abstract Syntax Notation One (ASN.1) Library

Unix/Linux:

• Open Secure Sockets Layer (SSL)
• Apache Web Server
• BIND Domain Name System (DNS) Server
• Remote Procedure Calls (RPC) Services
• Sendmail
• General UNIX Authentication Accounts with No Passwords or Weak Passwords
• Clear Text Services
• Simple Network Management Protocol (SNMP)
• Secure Shell (SSH)
• Misconfiguration of Enterprise Services NIS/NFS

These activities will not put an end to the viruses. But, it can reduce the damages caused by the viruses. The sudden hacks in the forms of viruses can also be mostly eliminated. Hope, his discussion on Viruses and Anti viruses may deliver a good knowledge about the protection from viruses.

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Optical mouse - Principle and working

What is a mouse?

The mouse is a pointing device which helps us to operate the computer. Unlike the complicated hardwares such as Mother board,RAM, Hardisk, Processor of the computer, the mouse is designed with a simple circuit to process. Now a days, we get varieties of mouse with different technologies in the market.

The developing applications in the computer field has not completely excluded the mouse yet. Although, we have switched to Touchpads in Laptops, "the function of mouse is easy and user-friendly when compared with touch pads for a new user", says the users. Mostly all the applications are operated with mouse for easy working. In recent days, the optical mouse had overcome the old ball mouse, because of its 'easy to use' function.

Disadvantages of Ball mouse

With the previous ball-rolled mouses, the movement of the pointer in the computer  is decided by the ball inside the mouse. So, if the ball gets damaged, or if dust gets clustered, the operation of the mouse becomes problem. When dust gathers, it takes some time to clear it too.With these disadvantages, the ball mouse was slowly moved away form the computer technology leaving the optical mouse to fill its space.

Working of Optical mouse

Now, almost everyone tries to switch from ball/roller mouse to Optical mouse. As the cost of the mouse is also being decreasing, the replacement is quiet quicker.To connect this optical mouse, the necessity is PS/2 or USB plug, and windows, macintosh or LINUX operating system installed in the computer.

The main components of the optical mouse are:

• Inbuilt optical sensor
• High speed camera which can take 1000 pictures at a time
• LED

These optical mouses do have an inbulit optical sensor. The optical sensor reads the movements of the optical mouse (moved by the user) with the help of the light rays which comes out from the bottom. ( The area in which a light glows). When the user moves the optical mouse, the LED (Light Emitting Diode) present inside the mouse emits the light according the minute movements. These movements are send to the camera as light rays. The camera captures the difference in light rays as images. When the camera captures the images, each and every pictures and compared to one another with the digital technology. With the comparison, the speed of the mouse and the direction of the movement of the mouse are rapidly calculated. According to the calculation, the pointer moves on the screen.

   

Comparison between a roller/ball  mouse and optical mouse

• The optical mouse does not have any movable parts as of the ball mouse. So, the life of the optical mouse is long compared to the ordinary mouse.
• Since the mouse works with the sensor recognition, the movements are clearly captured and so the moves gives out a same function in all moves.
• Since the ball is absent in the optical mouse, the weight of the optical mouse is less than that of the ball mouse.
• The dust clustering problem is abolished in the optical mouse as its parts are all static.
• The optical mouse can also function good without a mouse pad, which is impossible with ordinary mouses.Any way, optical mouses cannot be used above reflecting glasses or any glass materials.

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TFT LCD TV - Principle of working

What is TFT LCD?

The TFTLCD is explained as Thin Film Transistor Liquid Crystal Display. The Liquid Crystal Display’s which are used in famous LCD TV’s and TFTLCD TV’s are referred to as Nematic Phase liquid crystals. There lies a Thin Film(layer) Transistor arranged and so, it is called as  Thin Film Transistor Liquid Crystal DisplayThese Liquid crystals takes neither a solid or liquid form. The main difference between the LCD TV’s and the TFTLCD TV’s can be easily studied from the figure. Today's color LCD TVs and LCD Monitors have a sandwich-like structure as shown in figure 1. And also, in the LCD TV’s there is a single TFT panel.

What is TFT LCD TV and LCD Monitor Panel?

Figure shows a TFTLCD monitor. The only difference is that, the TFT LCD has a sandwich-like structure with liquid crystal filled between two glass plates. From the figure, we can see the TFT glass. This TFT Glass has as many TFT’s as the number of pixels displayed. The Color Filter Glass has color filter which generates color.

The Liquid Crystal Displays (LCD’s) have the tendency to change the properties of light passing through the crystals, when they are stimulated by some external electrical charge. With this property, the Liquid crystals move according to the difference in voltage between the Color Filter Glass and the TFT Glass. The amount of light supplied by Back Light is determined by the amount of movement of the liquid crystals in such a way as to generate color.

Structure of a color TFT LCD Panel

A TFT LCD module consists of a TFT panel, driving-circuit unit, backlight system, and assembly unit.

The main components of the TFT panel are:
1. LCD Panel
The LCD panel has - TFT-Array Substrate and Color Filter Substrate
The TFT-array substrate contains the TFTs, storage capacitors, pixel electrodes, and interconnect wiring and the - The color filter substrate contains the black matrix and resin film containing three primary-color - red, green, and blue - dyes or pigments. The two glass substrates are assembled with a sealant, and the gap between them is maintained by spacers, and LC material is injected into the gap between the substrates. Two sheets of polarizer film are attached to the outer faces of the sandwich formed by the glass substrates. A set of bonding pads are fabricated on each end of the gate and data-signal bus-lines to attach LCD Driver IC (LDI) chips.
2. Driving Circuit Unit
The Driving Circuit Unit is the main part which makes the TFTLCD TV’s to operate. It has LCD Driver IC (LDI) Chips, - Multi-layer PCBs and the - Driving Circuits to run.
3. Backlight & Chassis Unit 
This unit has the Backlight Unit and Chassis Assembly. The backlight is also the main cause for the clarity and resolution of picture.

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Mobile Phones - Principle of operation

A cellular/mobile system provides standard telephone operation by full-duplex two-way radio at remote locations. It provides a wireless connection to the Public Switched Telephone Network (PSTN) from any user location within the radio range of the system.

The basic concept behind the cellular radio system is that rather than serving a given geographical area within a single transmitter and receiver, the system divides the service area into many small areas known as cells, as shown in Fig. below. The typical cell covers only several square kilometers and contains its own receiver and low-power transmitter. The cell area shown in Fig. below is ideal hexagon. However, in reality they will have circular or other geometric shapes. These areas may overlap, and cells may be of different sizes.

Basic cellular system consists of mobile stations, base stations and a mobile switching center (MSC). The MSC is also known as Mobile Telephone Switching Office (MTSO). The MTSO controls '\11 the cells and provides the interface between each cell and the main telephone office. Each mobile communicates via radio with one of the base stations and may be handed off (switched from one cell to another) to any other base station throughout the duration of the call.

Each mobile station consists of a transceiver, an antenna and control circuitry. The base station consists of several transmitters and receivers which simultaneously handle full duplex communication and generally have towers which support several transmitting and receiving antennas. The base station serves as a bridge between all mobile users in the cell and connects the simultaneous mobile calls via telephone lines or microwave link to the MSC. The MSC co-ordinates the activities of all the base stations and connects the entire cellular system to the PSTN, most of the cellular system also provide a service known as roaming.

The cellular system operates in the 800-900 MHz range. The newer digital cellular systems have even greater capacity. Some of these systems operate in 1.7-1.8 GHz bands.

Cellular Telephone Unit

The Fig. below shows the block diagram of a cellular mobile radio unit. The unit consists of five major sections:

Transmitter, receiver, synthesizer, logic unit, and control unit. The mobile unit contains built-in rechargeable batteries to Provide operating power. The transmitter and receiver in the unit share the common antenna.

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Tips for Longer PC life

1. Keep your PC in a smoke-free environment. Tobacco smoke can damage delicate contacts and circuits. 

2. Leave your PC running. Powering up from a cold state is one of the most stressful things you can do to your system's components.
If you don't want to leave your PC running all the time, use Windows' Power Management settings to put your machine into hibernation rather than completely shutting down.

In Windows XP, right-click the desktop and select Properties. Click the Screen Saver tab and select the Power button. Choose the Hibernate tab to ensure that hibernation is enabled, and then select a time beneath "System hibernates" under the Power Schemes tab. 

(Note that this option is not available on all PCs.) 
Computers running older versions of Windows may or may not provide similar power-management features. Look under the Power Management icon (Power Options in Windows 2000) in Control Panel to evaluate your machine's capabilities. 

3. Don't leave your monitor running. The best way to extend your display's life is to shut it off when it's not in use.

4. Avoid jostling the PC. Whenever you move your system, even if it's just across the desktop, make sure the machine is shut down and unplugged.

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