Digital Bangladesh

What is a sound card?
Any software that uses sound needs a sound card. Listening to MP3 songs, playing computer games, watching movies from vcd, listening to songs from audio cds etc, requires a sound card. In a sound card the following components and features are usually found.
Components of a sound card

• Digital signal processor (DSP) this is an essential chip in the sound card
• Digtal to Analog Converter (DAC) This converter converts the digital music from cds etc to analog form, which the speakers can understand
• Analog to Ditial (ADC). This converter converts the analog signals from a microphone to a digital format that can be stored or transmitted by the computer.
• Musical Instrument Digital Interface (MIDI) This is a connecter used to connect the sound card to external MIDI devices such as a synthesizer, musical instruments.
• Game Port. This game port is integrated in the sound card to connect games related external devices such as Gamepad or Joystick.
• Line In or Line Out. These are used to connect devices such as speakers, head sets, microphones etc.

Buying tips for sound card
In todays computers, the sound cards are not external. Most of them are integrated within the motherboard. These are called Integrated motherboards. An external sound card ususally can be fitted to a PCI slot. They are Full Duplex type. Which means the sound card is capable of sending and receiving audio simultaneously. Therefore if you are buying external sound cards, do not buy the half duplex sound cards. These half duplex cards can only send or receive audio at a time. Many computer games requires DirectSound 3d. Therefore ask your dealer whether your sound card supports these before buying. Instead of buying 16 bit sound cards buy 24 bit or higher bit sound cards.

Documents and pictures can be converted into digital images using scanners. The price of scanners have tremendously fallen and is now affordable for any household. Therefore many would like to know about buying a scanner. MFD (Multi Function Device) are also available which integrates scanning, faxing and printing facilities all in one device. This report is about the scanner and its features.
Scanners are ranging from $100 to $1000. There are many models available both for office use as well as for home use.
How much resolution is needed for my scanner?
1. If you just need to scan documents or images occasionally and you are not too much concerned about high quality then a cheap low resolution scanner such as 600 dpi(dots per inch) can be selected.
2. If you need to scan documents from many different media and you are going to use it commercially and need many additional features then a scanner with medium resolution such as 1200 dpi will be suitable for you.
3. If you have to scan things like ‘negative’s or you would like to use the OCR feature then you have to buy a high resolution scanner such as 2400 dpi
Some tips to buy the right scanner

1. The price of the scanner is directly proportional to the optical resolution of the scanner. For example a scanner with 1200×600 resolution will be cheaper than 1200×2400 and so on.
2. Also check the ‘color depth’ of the scanner. A 36 bit color depth scanners are now obsolete. 42 bit and 48 bit scanners are mostly available. It is better to choose a scanner with 48 bit color depth.
3. Check which PORT the scanner supports. Most of the modern scanners use USB. Some scanners have SCSI interface. So before you buy the scanner check whether your computer has USB port to connect the scanner.
4. Check that the scanner comes with all the required cables to connect to the computer
5. Check whether ‘onsite support’ is provided. If not you may have to carry the scanner to the dealer if it doesn’t work.
6. If your main intention of buying a scanner is to scan from books (big) then check whether the top cover can be detached or there is a provision to lift the cover to 3 inches atleast.
7. If you would like to scan a document, import it to MS Word and then edit the document then you need the OCR (Optical Character Recognition) software. So check whether the scanner comes with the OCR software CD. Some scanners do not come with this software. If you would like to have this then choose a scanner that does come with the CD.
8. If you would like to scan ‘negatives’ then you need to buy a ‘Transparence Adapter’. See whether you can connect this to the scanner.
9. If you would like to scan a large collection of documents automatically without manual intervention then you need to buy the ‘Automatic Document Feeder’ (ADF). See that the scanner you choose supports this so that the ADF can be connected to your scanner.

Control buttons in a scanner
There are many buttons in a scanner. FAX, Print/COpy, Email, OCR, CD an Web are some of the buttons. Your scanner may or maynot hav all of these buttons. Let us see what are these buttons for.

1. If you would like to scan a document and at the same time FAX the document to a FAX number then ‘Scan to FAX’ can be used. You need not have a separate FAX machine.
2. If you need to scan and at the same time print the document or save a copy of the document as a file in your computer then the ‘Scan to Print/Copy’ button can be used.
3. ‘Scan to email’ is used to scan and send the document to any email address. On pressing this button your favourite email client such as ‘outlook’ will start and the scanned document will be attached to the email. You just need to enter the email address and send.
4. ‘Scan to OCR’ is used to scan the document and open it in your OCR software to edit.
5. The same goes for ’scan to cd’ to write the scanned document to a CD and ‘Scan to Web’ is used to publish to a website after scanning.

Every PC user spends atleast 5 hours looking at the monitor every day. If the picture is not clear enough then there is a high possibility that the eyes get damaged. There are many different sizes of monitors available ranging from 15″ to 17″ or even higher. The sharpness of the image in a monitor is dependent on the Graphics card. Nevertheless the quality of the monitors play an important role. Here are some of the tips that you should know before buying a monitor.

1. There are two types of monitors namely CRT and LCD. The monitor that looks like a small TV is a CRT monitor. In TV as well as CRT monitors there is a Cathode Ray Tube. An LCD monitor is smaller in width and consumes less power.
2. The 15″,17″ or 19″ TVs represent the diagonal length of the screen. Therefore if you buy a 15″ inch screen , the actual length is just 13 1/2 or 14 inches only.
3. CRT monitor is heavier than LCD monitor. LCD monitor is very lightweight.
4. The distance between two adjacent pixels in a monitor is called ‘dot pitch‘. This is measured in millimeters (mm). Smaller the dot pitch the clearer the picture quality. Usually there are monitors with dot pitch varying between 0.20 mm to 0.27mm. Some manufacturers use diagonal dot pitch while most of them use horizontal dotpitch. The diagonal dot pitch is always longer than the horizontal dot pitch
5. Resolution of a monitor has to be considered with care. Most of the monitors have resolution of 800×600 and 1024×768. The more expensive monitors have 1280×1024 and 1600×1200 resolutions. When the resolution is higher the images and text will appear smaller. But you can see more text and bigger pictures in the monitor with high resolution.
6. Another thing to note is the ‘Refresh rate‘. This rate is usually 73 Hz, 75 Hz, 85 Hz. Refresh rate of 85 Hz means the picture on the monitor is refreshed 85 times within a second.
7. The brightness and contrast can be adjusted using buttons. Some monitors come with the software to adjust these settings.

The use of virtual memory is not visible to the PC user. Which means while working at the computer we will not know whether the virtual memory is being used as there will be no indication.
The reason will be obvious if you know how virtual memory functions. Usually the RAM memory in computers are now either 256 or 512 MB. Some computers also have 1Gb RAM memory.
But this RAM size is not sufficient for most of the tasks that we do in computers. For example after we start the computer and open MS Word and MS outlook, then the RAM memory is occupied by these applications. Therefore if we open more applications without closing the existing applications then the RAM memory is not enough.
While opening another application, the operating system will see which are the applications currently not in use and then move those unused applications to the hard disk temporarily. Therefore temporarily the RAM memory is free and can be used by this new application. This happens automatically by the operating system and therefore not visible to the PC user. This is called virtual memory.

Some tips to save money while using Inkjet Printers
In early days of computer history everyone used a dot matrix printer. Only Printing presses, publishers and DTP designers used a laser printer. In those days the price of a laser printer was very expensive and was not affordable for small businesses and home users. Inkjet Printers were introduced at affordable prices for small businesses and home users. But those who bought inkjet printers would agree that though the inkjet printers were cheap, the inkjet printer cartridges are not cheap. These cartridges have to be constantly refilled or replaced after printing a number of pages. Buying new inkjet printer cartridges every time is very expensive and unaffordable. But instead of buying new cartridge everytime you can refill the ink in the same cartridge and save a lot of money. but even refilling has to be done carefully as there are many who cheat.
In dot matrix printers, the cost of printing a page is very less. If the printing quality is not good then you can change the ink ribbon for 1 or 2 dollars and you can start printing again in dot matrix printers. But the quality of printing in dotmatrix printer cannot compare with the high quality of printing in inkjet and laser printers.
But changing cartridges in inkjet printers is very expensive. For example, a HP black inkjet cartridge costs around $20 to $30. The price of an EPSON inkjet printer cartridge is around $10 to $20. Lexmark cartridges are even more expensive than the HP cartridges. Because of these high costs people prefer the refill options. A cartridge can be refilled atleast 6 to 8 times. Many use this cheaper refilling option and save money.
The size of a cartridge is usually 10ml to 20ml based on the inkjet printer model. You can buy a 1 litre black ink bottle for less than $30. Assume that the cartridge size is approximately 20ml, then you can refill this cartridge atleast 40 times. So in effect you are only spending less than a dollar for a cartridge.
Even color inkjet cartridges can be refilled at around the same price. The color cartridges can hold less amount of ink but there are three colour cartridges. Approximately they can hold 5ml to 7 ml of ink. Each color cartridge costs around $25 for a one liter bottle. The machine used to refill this ink costs around $120.
If you need more details on refilling cartridges and want to know the companies who do this business just search in google for the term ‘Inkjet cartridge refilling’.

Though there are not many left handed computer users, it is a bit difficult for a left handed person to use a computer mouse. From Windows 98 onwards it is possible to configure the mouse to suit a left handed user. Once you configure your mouse the left handed users can swap the functionality of a left and right mouse button. To do this follow these steps:
To configure mouse for left handers in Windows 98

1. Click Start->settings and open ‘Control panel’
2. In the control panel double click the ‘mouse’ icon
3. In this screen, in the buttons tab select the ‘Lefthanded setting’ and click OK.

To configure mouse for left handers in Window XP

1. Click Start and open ‘Control panel’
2. In the control panel click “Printers and Other Hardware’ section.
3. Then select the ‘Mouse’ section
4. In the ‘Buttons’ tab make the following selections
5. For ‘Left Button’ choose ‘Shortcut Menu’
6. For ‘Right Button’ choose ‘Click’
7. Now click on ‘OK’

Now your mouse will be set for use by a left hander.

We all use many devices and equipments that run on electricity. Some of these equipments are also electronic devices. For all these to function properly they need uniform power supply. The electric supply in many countries is not uniform. Therefore to make it uniform there is a need for a device. There are many such devices available in the market today. For example UPS (Uninterrupted power supply), Voltage Stabilizer, Constant Voltage Transformer are such devices available today. What is the use of these devices. How to they work? Which of these devices is suitable for you? You will get answer to all these questions in this tutorial.
What is power conditioning?
We can never guarantee that we will get constant power supply. The power supply always has fluctuations. Spikes, Surges, Brownouts, Blackouts and Noise can damage your electrical appliances especially your computer. To prevent this from happening you need a device that does power conditioning.
What is the meaning of Spikes and Surges?
Electricity has to be uninterrupted. If the voltage is higher than the specified level then it is ‘Over Voltage. If the voltage is lower than the specified level then it is ‘Under Voltage’.
Both Spike and Surge come under ‘Over Voltage’ category. But there is a small difference between spike and surge. If there is very high voltage for an instant but comes back to normal immediately then it is called ‘Spike’. This is also referred as ‘Impulse’. If there is very high voltage for a slightly longer period (eg. 1/20 th of a second) then it is called ‘Surge’.
What is Brownout, blackout, Sags and Line Noises?
If the voltage is dangerously reduced to very low within a short period of time then it is called ‘Brownout’. This is also referred as ‘Sags’. When this happens, the computers can be seriously damaged.
If the power supply is totally cut then it is called ‘Blackout’. Noises can mix with electromagnetic or radio waves or any signals. This is called ‘Line Noises’. This may also reduce the voltage level to very low within a short period of time.
What do you need to do Power conditioning.
There are many devices such as Surge Supressors, Spike Busters, Isolation Transformers, Servo Stabiliser, Constant Voltage Transformers or Uninterruptible Power Supply System. We can choose the most suitable power conditioning device based on the equipment we are going to use and based on the quality of our electrical power supply.
Which power conditioning device is best?
The best power conditioning device is the UPS (Uninterrupted Power Supply). This is capable of handling Spikes, Surges, Brownouts, Blackouts etc.
How can UPS provide power supply when electrical supply is cut?
Many have this doubt. UPS has an internal battery. With this battery charger and an Inverter is also present in an UPS. The inverter converts the ‘Direct current’ supplied by the battery to ‘Alternatinc current’ as required by the computer. When there is electrical supply the battery charger charges the internal battery. When there is a power cut, the battery supplies DC which is converted to AC by the inverter and power is supplied to computer.
What if the battery loses its power?
When there is power cut, the required power is taken from the battery. Therefore the battery keeps losing its capacity. If the power supply comes back before the battery is fully flat then the battery charger will start recharging the drained battery.
But if the power supply doesn’t come back then the battery keeps supplying until it totally drains out. When the battery drains below a certain level the UPS sounds an alarm for your to shut down your computer and turn off the power and turn off UPS.
How long can an UPS supply power when there is no power?
This depends on the backup time of your UPS. If your UPS has 30 minutes backup then your UPS can supply power for 30 minutes of the power is cut. The higher the backup time of UPS the more expensive.
What other tips for buying UPS?
The backup time of your UPS is the most important you need to consider. Other than that, you should know how many KVA (Kilo Volt Ampere) your UPS has. A computer needs atleast 0.5 KVA to function. If you are planning to connect more than one computer to a single UPS then you need to get an UPS with higher KVA.
What type of battery is used in an UPS?
UPS uses ‘SMF’ batteries (Sealed Maintenance Free). These type of batteries can be used for 5 to 7 years continuously.
What are the different types of UPS?
There are three types of UPS namely Online, Offline and Line Interactive. ‘Offline UPS’ directly supplies the electrical supply to the computer without any changes. Only if there is a power cut, the ‘Offline UPS’ takes over. But ‘Online UPS’ even if there is power supply it will always supply power from the battery and the power supply is used to continously recharge the battery. ‘Interactive UPS’ always supplies uniform current by using Ferroresonat Transformer.
Which UPS is cheaper?
Obviously, offline UPS is the cheapest. Online UPS is very expensive. Interactive UPS is between the offline and online.
Can I connect printer to UPS?
It depends on the UPS capacity and the type of printer. Generally laser printer should not be connected to the UPS. Other printers can be connected. But you should have a higer KVA UPS to support.