Printers,+Monitors,+Speakers,+Projectors

=Strand 3:IT Systems=

Printers, Monitors, Speakers, Projectors
Monitor ** What is a monitor? ** Monitor displays the video and graphics information generated by the computer through the video card. Monitors are very similar to televisions but display information at a much higher quality.

Examples of Monitors are: CRT monitors, being based on the technology used to create standard definition television screens Disadvantages are: · They take up a lot of space · Uses more electrical power than LCDs · Generates excess heat Advantages are: · The contrast ratios and depths of colors displayed were much greater with CRT monitors than LCDs
 * Cathode Ray Tube (CRD) ** - monitors are the large bulky monitors that are gradually being phased-out of production, as they are costly to manufacture.

LCD monitors are less-bulky and are cheaper to manufacture. As the computer monitor is increasingly at the centre of consumer entertainment systems, and is used not only for Word processing and browsing the web, but also for gaming and watching movies. Disadvantages are: · More expensive than CRTs · Screen care and fragility. LCD monitors may be slim, but they're also more prone to damage and screen breakage. · Native resolution. LCD monitors can only display information well at the resolution they were designed for. At any other resolution, image quality will suffer. · Viewing angles. Looking at an LCD monitor from an angle causes the image to look dimmer or even disappear completely. · Colors. The color accuracy of an LCD monitor does not match that of a CRT monitors. Advantages are: · Uses Less Power. LCDs also produce less heat, which means less load on air conditioning. · Takes up less space. LCD monitors are small, thin, and weigh less. · Highly adjustable. Many LCD models can be rotated 90 degrees, allowing you to view websites in portrait mode. LCDs can also be mounted on the wall or on an arm. · No flicker. LCDs don't have lines that need to be scanned like in CRTs. No flicker = a lot less eye strain. · Less glare. Due to the material of the LCD screen, less light is reflected at the user. Same with "no flicker", this results in less eye strain. · Brightness. LCD monitors are brighter than the traditional CRTs.
 * Liquid Crystal Display (LCD) ** - monitors are the successor to CRT displays.

Printers **What is a printer?** A printer is a device that accepts text and graphic output from a computer and transfers the information to paper, usually to standard size sheets of paper. Printers are sometimes sold with computers, but more frequently are purchased separately. Printers vary in: · size · speed · sophistication · cost In general, more expensive printers are used for higher-resolution color printing. The four printer qualities of most interest to most users are:

Examples of printers are:
 * Color: ** Color is important for users who need to print pages for presentations or maps and other pages where color is part of the information. Color printers can also be set to print only in black-and-white. Color printers are more expensive to operate since they use two ink cartridges (one color and one black ink) that need to be replaced after a certain number of pages. Users who don't have a specific
 * need for color and who print a lot of pages will find a black-and-white printer cheaper to operate.
 * **Resolution:** Printer resolution (the sharpness of text and images on paper) is usually measured in dots per inch ( dpi ). Most inexpensive printers provide sufficient resolution for most purposes at 600 dpi.
 * **Speed:** If you do much printing, the speed of the printer becomes important. Inexpensive printers print only about 3 to 6 sheets per minute. Color printing is slower. More expensive printers are much faster.
 * **Memory:** Most printers come with a small amount of memory (for example, one megabyte) that can be expanded by the user. Having more than the minimum amount of memory is helpful and faster when printing out pages with large images or tables with lines around them (which the printer treats as a large image).
 * Dot matrix printer** which is a low-cost personal computer printer. It’s an impact printer that strikes the paper a line at a time.
 * Inkjet printer** is a non-impact printer. It sprays ink from an ink cartridge at very close range to the paper as it rolls by.

Speaker

A speaker is an electro acoustic transducer meaning it converts an electrical signal into sound. The speaker moves in harmony with the variations of an electrical signal and causes sound waves to spread through a medium such as air or water. The term "loudspeaker" may refer to individual transducers known as drivers or to complete speaker systems consisting of an enclosure including one or more drivers. To reproduce a wide range of frequencies, most loudspeaker systems employ more than one driver, particularly for higher sound pressure level or maximum accuracy. Individual drivers are used to reproduce different frequency ranges. The drivers are named
 * subwoofers for very low frequencies
 * woofers low frequencies
 * mid-range speakers’ middle frequencies


 * tweeters high frequencies

Projector A projector takes a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other inconsistencies through manual settings. Video projectors are widely used for conference room presentations, classroom training, home theatre and live events applications. Projectors are widely used in many schools and other educational settings, connected to an interactive white board to interactively teach pupils.

A projector, also known as a Digital Projector, may be built into a cabinet with a rear-projection screen to form a single unified display device, now popular for “home theater” experience. The cost of a device is not only determined by its resolution, and also by its brightness. A projector with a higher light output is required for a larger screen or a room with a high amount of light. A rating of 1500 to 2500 ANSI lumens or lower is suitable for smaller screens with controlled lighting or low ambient light. Between 2500 and 4000 lm is suitable for medium-sized screens with some ambient light or dimmed light. Over 4000 lm is appropriate for very large screens in a large room with no lighting control for example, a conference room. Projected image size is important; because the total amount of light does not change, as size increases, brightness decreases. Image sizes are typically measured in linear terms, diagonally, obscuring the fact that larger images require much more light. Increasing the diagonal measure of the image by 25% reduces the image brightness by 35%; an increase of 41% reduces brightness by half.