Displays are a popular peripheral device. They allow users to see output from the computer. There are many different sizes and types. There are many different ways that we can connect these devices.
The connections are key to what is possible with our displays. VGA or video graphics array is a connection that uses a 15 pin D type connector. 15 pin d connector. VGA uses a the DE-15 which has 3 rows of 5 pins. Sometimes the VGA is called a DB-9 connection but a DB-9 has only 9 pins and is used as a serial connection for legacy devices. VGA use an analog signal. The signal starts to degrade at 30 meters at low resolutions and at only 5 meters at high resolutions. VGA does not have any DRM (digital rights management) support. DVI (digital visual interface) superseded VGA. DVI supports only video and no video. There are a few different types of connectors depending on the type of DVI. DVI-A uses an analog signal and a 16 pin D style connector. A DVI-A cable can be converted into VGA without any signals be changed. DVI-D uses digital signals and does not support analog signals. DVI-D uses both a 24 pin and 28 pin D style connector. DVI-I and use both analog or digital signals. The “I” in DVI-I stands for integrated. DVI-I uses both a 22 pin and 28 pin connector. DVI supports 15 meter cables at low resolutions and 5 meter cables at high resolution. DVI does support DRM. HDMI stands for High-Definition Multimedia Interface. HDMI uses a signal that is digital. It uses a 19 pin connection for type A, C, D and E. It uses a 29 pin connection for the type B. The type A connector is the standard size HDMI, the type B connector was a duel-link and was never actually used, the type C connector is the mini HDMI, the type D connector is the micro HDMI, and the type E is used in automotive connections. The HDMI alternative mode also supports the USB-C connection. The signal for HDMI starts to degrade at 5 meters. It supports both video and audio. HDMI also supports DRM. DisplayPort allows for a higher bandwidth than HDMI. DisplayPort uses a 20 pin connector for the full size connection and the mini connection. It supports both audio and video. DisplayPort signals start to see degradation at 3 meters.
There are two main display types in use today and those are LCD and LED. LCD monitors use CCFL (cold cathode fluorescent lamp) as the back light that were either placed at opposite end of the LCD screen or as an array of CCFLs placed behind the LCD screen. This makes them more bulky than LED monitors that use LEDs as the back lighting. LCDs require more power, usually have a shorter life time, and suffered from higher latency. CCFLs also have a very high electromagnetic interference. TN, or twisted nematic, displays were the first widely used LCD monitors. They were the first flat screen display and boosts of shorter response times, a high brightness, and lower power draw compared to other LCD monitors. TN displays did not have very good viewing angles and the colors were not as good. IPS (in-line plane switching) LCDs tried to overcome the drawbacks of TN displays. IPS displays are LCDs that have better viewing angles, better color, and lower contrast ratios. This comes at a cost of a lower refresh rate. LED displays have a LED matrix placed behind the screen. There are two types of LEDs that are used and they are white LEDs and RGB (red, green, blue) LEDs. LED displays have a significantly lower power draw. LEDs are capable of having faster response times that LCDs. TFT (thin film transistors) allows there to be a transistor on each pixel. This allows for higher quality displays. Displays use AC (alternating current) so your monitor can be plugged to the wall without an inverter. Laptops on the other hand have to convert the AV power from the wall into DC (direct current) to be used by the circuitry and then has to be inverted again to AV power for the display. The OSD (on screen display) message is used to prevent burn-in on the display. Burn-in is when a static image is displayed on a screen and then will be present on the display even after the image is changed. The OSD message usually will come on after a display has detected that the image has not changed after a period of time. The indicator light is usually on the front of the monitors. If the light is amber that usually indicates that the monitor in in a low power state and either cannot detect a source or some monitors will go into a low power state if the OSD message has been displayed after a set amount of time. A green or blue light usually indicates that the monitor is displaying the output of the connected device.
Resolution is how many pixels are on the display. It is usually shown as horizontal pixels x vertical pixels. The aspect ratio is the width:height in physical display measurements. Because LCD and LED monitors all have fixed resolutions, the aspect ratio can be calculated with the native resolution reduced down to the smallest whole numbers. The three most popular aspect ratios are 4:3, 16:10, and 16:9.
| VGA | SVGA | XGA | WXGA | SXGA | UXGA | 2K | QXGA | Standard HD | Full HD | 4K UHD | Full 4K UHD | Full 8K UHD |
| 640×480 | 800×600 | 1024×768 | 1280×720 1280×768 1366×768 | 1600×900 | 1600×1200 | 2048×1080 | 2048×1536 | 1280×720 | 1920×1080 | 3840×2160 | 4096×2304 | 8192×4608 |
Troubleshooting display types is important to know. Always remember: Simple fixes first! Use the indicator light on the monitor to help you. If the image is in the wrong resolution there are a few reasons it could be that way. The computer could be in VGA mode because the video driver is not working or installed, the device booted in recovery or safe mode, or the resolution is just not set correctly in settings. If there is no image you should check power, check cables, check for a OSD message, check the source on the monitor, and check the indicator light on the monitor. If there is a dim display the brightness settings in OS or on display could be turned down, the inverter could be dead, or the back light could of burnt out. If the display is over heating you should check the vents for any debris and make sure there is enough air flow. If you suspect a dead pixel, you can load a totally white screen and look for abnormalities in coloring. If you have a dead pixel, unfortunately you have to replace the unit. If you have stuck pixels you can run a display calibration software or sometimes a pencil eraser really lightly pressed and twisted on the pixel will fix it. If you have artifacts on the screen it could be a video format or compression issue, the video card could be over heating or damaged, maybe the driver isn’t up to date, missing or corrupted. If you have a flickering image, it could be a loose connection, a bad or damaged cable, or maybe even a damaged port. When troubleshooting always remember to question the obvious.
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