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Output is the data that has been processed into a useful form.
Output device is any type of hardware component that conveys information to one or more people.
Display device is an output device that usually conveys texts, graphics, and video information.
Monitor – (visual display unit)
a display device that is packaged as a separate peripheral
Types of monitors:
1. Cathode Ray Tube (CRT) (15”-22”)
-Until the early 1980s, they were known as video display terminals and were physically attached to the computer and keyboard.
-It was monochrome and the image quality was poor.
-Is more affordable than LCD
-Can accommodate many different resolutions (RESOLUTION - number of pixels displayed on screen at one time)
>capable of generating a resolution up to 2048 x 1536 pixels, thereby providing a clear picture quality
> This is referred to as multisync by the industry. By adjusting the electron beam in the tube, the screen can easily be adjusted downward to lower resolutions while keeping the picture clarity intact.
-Good for graphical details
-has high refresh rates
but
-is heavier than LCD’s.
-take up a lot of spaces
-cost more to run and get heated up very easily
- cannot project an image to the edges of the full size tube
- The size and weight of an LCD monitor can be upwards of 80% lighter than an equivalent dimension CRT screen
ACQUISITION:
-if acquiring CRT, check the:
-Screen size – measured diagonally from the lower corner to the opposite side upper corner. However, the monitor size does not translate into the actual display size.
-Resolution - Here is a listing of some of the more commonly used resolutions along with the acronym for that resolution:
SVGA = 800x600
XGA = 1024x768
SXGA = 1280x1024
UXGA = 1600x1200
-Dot Pitch - Many manufacturers and retailers tend to not list the dot pitch ratings anymore. This rating refers to the size of a given pixel on the screen in millimeters. This tended to be a problem in past years as screens that attempted to do high resolutions with large dot pitch ratings tended to have a fuzzy image because of the color bleeding between pixels on the screen. Lower dot pitch ratings are preferred as it gives the display greater image clarity. Most ratings for this will be between .21 and .28 mm with most screens having an average rating of about .25 mm.
-Refresh rates- The refresh rate refers to the number of times the monitor can pass the beam over the full area of the display. This rate can vary widely depending upon the settings the user has on their computer and what the video card that is driving the display is capable of. All refresh ratings by manufacturers tend to list the maximum refresh rate at a given resolution. This number is listed in Hertz (Hz) or cycles per second. For example, a monitor spec sheet may list something like 1280x1024@100Hz. This means that the monitor is capable of scanning the screen 100 times per second at the 1280x1024 resolution. So why does refresh rate matter? Viewing a CRT display over long periods of time can cause eye fatigue. Monitors running at low refresh rates will cause this fatigue in a shorter amount of time. Typically, it is best to try and get a display that will display at 75 Hz or better at the desired resolution. 60 Hz is considered the minimum and is the typical default refresh rate for video drivers and monitors in Windows.
Screen Contour
CRT displays now have a wide variety of contours to the front of the screen or tube. Original tubes similar to TV sets had a rounded surface to make is easier for the scanning electron beam to provide a clear image. As technology progressed, flat screens arrived which still had the contour on the left and right but a flat surface vertically. Now CRT monitors are available with perfectly flat screens for both horizontal and vertical surfaces. So, what does the contour matter? Rounded screen surfaces tend to reflect more light causing a glare on the screen. Similar to low refresh rates, large amounts of glare on a computer screen increases the amount of eye fatigue.
-viewing angles- Indicates how far you can move to the side of (or above and below) the center of the screen and still see what's displayed
2. A flat-panel display is a lightweight display device that typically uses liquid crystal display.
Types:
a. Liquid Crystal Display (LCD) (14”, 30”, 40”)
-is a desktop monitor that uses LCD to produce images. It produces sharp, flicker-free images.
-Throughout the 1990s the primary use of LCD technology as computer monitors was in laptops where the lower power consumption, lighter weight, and smaller physical size of LCDs justified the higher price versus a CRT.
-Uses a liquid compound to present information on a display device. Typically contains fluorescent tubes that emit light waves forward the liquid-crystal cells, which are sandwiched between two sheets of material. When an electrical charge passes through the cells, the cells twist. The twisting causes some light waves to be blocked and allows others to pass through, creating images on the display. Uses either passive/active-matrix.
1. active-matrix display also known as a TFT (thin-film transistor), uses a separate transistor to apply charges to each liquid crystal cell and thus displays high-quality color that is viewable from all angles.
2. A passive-matrix displays uses fewer transistors, requires less power and is less expensive than the other one. Users view images on it best when working directly in front of it.
-Less desk space needed. It’s smaller and lighter.
-Produces less eye fatigue to the user. The constant light barrage and scan lines of a CRT tube tend to cause strain on heavy computer users. The lower intensity of the LCD monitors coupled with their constant screen display of pixels being on or off produces less fatigue for the user.
-Require less power to run, more environmentally friendly
-Increased Viewable area, a 15"LCD can give the same viewable area as a 17" CRT monitor
But
-Viewing angle can affect image quality
-One native resolution. An LCD screen can only display the number of pixels in its matrix and no more or less. It can display a lower resolution in one of two ways. Using only a fraction of the total pixels on the display or through extrapolation. Extrapolation is a method whereby the monitor blends multiple pixels together to simulate a single smaller pixel. This can often lead to a blurry or fuzzy image particularly with text when running the screen below is native resolution.
-More expensive than a CRT
-some LCD Monitors has lower response time. Some are improved but it caused another problem which is reduced color clarity.
LCD quality:
-resolution is the number of horizontal and vertical pixels in a display device. Pixel (short for picture element) is a single point in electronic image
LCDs are geared for a specific resolution called native resolution.
Here are some of the common native resolutions found in LCD monitors:
· 17" (Widescreen): 1280x800 (WXGA)
· 19" (Widescreen): 1440x900 (WXGA+)
· 21" (Widescreen): 1600x900 (WSXGA+)
· 22" (Widescreen): 1920x1080 (WUXGA)
· 24" (Widescreen): 1920x1080 (WUXGA)
· 27" (Widescreen): 2560x1440 (WQHD)
· 30" (Widescreen): 2560x1600
Currently the most popular screen resolution is 1024 x 768 or higher.
-response time of an LCD monitor is the time in milliseconds that it takes to turn a pixel on or off. LCD monitors' response times range from 3 to 16 ms.
-brightness of an LCD monitor is measured in nits (unit of visible light intensity equal to one candela per square meter. candela (standard unit of luminous intensity) the higher the nits, the brighter the images.
-dot pitch/pixel pitch is the distance in millimeters between pixels on a display device. text created with a smaller dot pitch is easier to read. The lower the number, the sharper the image.
-contrast ratio describes the difference in light intensity between the brightest white and darkest black that can be displayed on a monitor. Higher contrast ratios represent colors better.
B. a plasma monitor is a display device that uses gas plasma technology, which sandwiches a layer of gas between two glass plates. When voltage is applied, the gas releases UV light. This UV light causes the pixels on the screen to glow and form an image. It offers screen sizes up to 150 inches wide and richer colors than LCD monitors but is more expensive.
In acquiring monitors, also consider:
Panel Coatings
· This is something that most people don't think about much primarily because the market may not give them much choice. The coatings of the display panel fall into two categories:
· anti-glare (computer screen) comes in the form of a sheet of plastic that clings to the screen
- has two types
1. Matte finish display – scatters light rather than allowing it to reflect off a smooth surface. Cuts down the amount of light that reflects off the display. It also has advantages such as making the display of image blurry;
2. Glossy - uses a chemical coating over a smooth surface to cut down glare. -have vibrant colors and the highest contrast and brightness because they have a smooth, high-gloss surface. As a result, it is often the choice for movies or gaming. However, strong lighting causes glare on this screen which is very annoying and may tire your eyes if you have to stare at it all the time. You can also see reflections on the screen. Some graphics designers may also find the colors inaccurate. Glossy will work great for you if the lighting in your room doesn't create any glare on the screen.
*choosing:
Consider the environment in which you will be using the computer.
Matte - well-suited for home use, where there is mostly ambient light that you can control.
Glossy - will work great for you if the lighting in your room doesn't create any glare on the screen.
The majority of monitors for consumers use a glossy coating. This is done because it tends to show off colors better in low light conditions. The downside is that in brighter light it generates glare and reflections. You can tell most monitors with glossy coatings either through the use of glass on the outside front of the monitor or through terms such as crystal to describe the filters. Business oriented monitors tend to come with anti-glare coatings. These have a film over the LCD panel that helps reduces reflections. It will slightly mute the colors but they are much better in bright lighting conditions such as offices with overhead fluorescent lighting.
A good way to tell which type of coating work best for your LCD will monitor is to do a small test where the computer is going to be used. Take a small piece of glass such as a picture frame and place it where the monitor would be with the lighting that will be used when the computer is. If you see a lot of reflections or glare off the glass, it is best to get an anti-glare coated screen. If you don't have the reflections and glare, then a glossy screen will work fine.
Viewing Angles
LCD's produce their image by having a film that when a current runs through the pixel, it turns on that shade of color. The problem with the LCD film is that this color can only be accurately represented when viewed straight on. The further away from a perpendicular viewing angle, the color will tend to wash out. The LCD monitors are generally rated for their visible viewing angle for both horizontal and vertical. This is rated in degrees and is the arc of a semicircle whose center is at the perpendicular to the screen. A theoretical viewing angle of 180 degrees would mean that it is fully visible from any angle in front of the screen. A higher viewing angle is preferred over a lower angle unless you happen to want some security with your screen. Note that the viewing angles still may not translate fully to a good quality image but one that is viewable.
Connectors
Most LCD panels have an analog and a digital connector on them. The analog connector is the VGA or DSUB-15. HDMI is now becoming the most common digital connector thanks to its adoption in HDTVs. DVI was previously most popular computer digital interface .DisplayPort and its mini version are now becoming more popular for high end graphics displays. Thunderbolt is Apple and Intel's new connector that is fully compatible with the DisplayPort standards. Check to see what type of connector your video card can use before buying a monitor to ensure you get a compatible monitor. You still may be able to use a monitor with a different connector than your video card by using adapters but they can get fairly expensive. Some monitors may also come with home theater connectors including component, composite and S-video.
Speakers
Speakers are attached to computers for the output of sound. Sound cards are required in the computer for speakers.
Classification of Speakers:
1. Internal – built in speakers.
- A very basic speaker found on the computer motherboard.
2. External – a separate set of speaker.
*important terms:*
>Satellite speakers are the speakers that carry the mid-bass on up in a three piece system that consist of a pair of "small" speakers (the satellites)
>Sub-woofer – Woofer is the term commonly used for a loudspeaker driver designed to produce low frequency sounds, typically from around 40 hertz up to about a kilohertz or higher.
Different Types of Computer Speakers
PC Speakers
The most conventional speakers found in the primitive IBM machines.
The most conventional speakers found in the primitive IBM machines.
Multi-channel Speakers
The new age speakers where the channels represent the output devices. This new generation speakers are exceptional on sound quality but are on the higher side of the budget.
5.1 Speaker
7.1 Speaker
Standard Speakers
The standard speakers are nothing but the normal 2.1 channel or 2 channel speakers. These are the most popular type of speakers with generating enough sound required by a home or corporate user. The standard speakers are cheap and easily installable with limited wiring compared .
Standard Speakers
The standard speakers are nothing but the normal 2.1 channel or 2 channel speakers. These are the most popular type of speakers with generating enough sound required by a home or corporate user. The standard speakers are cheap and easily installable with limited wiring compared .
USB speakers
There are also USB speakers which are powered from the 5 volts at a few milliamsp provided by the USB port, per the standard. The USB powered amplifier draws the power through a USB cable/plug. No batteries or AC power source are required.
There are also USB speakers which are powered from the 5 volts at a few milliamsp provided by the USB port, per the standard. The USB powered amplifier draws the power through a USB cable/plug. No batteries or AC power source are required.
Wireless
More recently, wireless speakers have allowed users to avoid the mess of wires associated with surround sound speaker setups. While these are excellent for many users, they can often conflict with a home Wi-Fi network.
There are three main computer stereo cables.
1. RCA Cable Plug – Right (White or Black) Left (Red)
2. 1/8 inch – 3.5mm mini stereo plug.
3. Single plug and play USB cables – hot swapping
*note: it all depends on the brand and the model of speaker*
Specifications
Sound pressure level (SPL) that the speaker can deliver. | |||
Typical design power used for driving the speaker. | |||
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Input impedance for a speaker is optimally matched to the output impedance of the driving amplifier for most efficient and truest sound replication. | |||
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The frequency response, or dynamic range, is the range of frequencies over which the speaker will operate while still meeting its performance specifications. | |||
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Nominal size of speaker; diameter or width for round or square speakers, shorter dimension for rectangular or oval speakers. | |||
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Weight of speaker, including any enclosure or attached features. | |||
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Features
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Your choices are... | |||
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Application
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Your choices are... | |||
Active noise cancellation | |||
Designed for use in aircraft. | |||
Speakers for radio or audio systems in cars, trucks, and other vehicles. | |||
Professional grade audio speaker components and/or systems for use in recording studios or television and radio broadcast facilities and equipment. | |||
Designed for use with computers or industrial workstations. | |||
Any consumer electronics application, including video games, television speakers, consumer-grade radios, toys, etc. | |||
Designed for installation in headsets, helmets, earphones, etc. | |||
Designed and constructed for use in public address systems or installation in public facilities. | |||
Suitable for use in the reproduction of high fidelity audio and music sound. | |||
Designed for use in applications such as intercom systems, security access stations, and/or intraoffice paging or communications. | |||
Designed for use with telephones and other voice communication products. | |||
Other unlisted, specialized, or proprietary application. | |||
Inputs received by the speakers:
1. Analog
2. Digital - most common