Video and monitor terms

I have collected here descriptions of vidoe terms related to computer video technology and monitors.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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A

B

BNC: A connector used for connecting coaxial cables to monitor.

C

Cathode Ray Tube: The picture tube type used in normal computer monitors.
Characteristic impedance: The characteristic impedance describe the high frequency characteristics of the coaxial cable. The coaxial cables used with computer monitors and video systen have a characteristic impedance of 75 ohms, which means that those cables look like 75 ohm load to the high frequency signal and the system works best when the both ends of the cable are terminated with 75 ohm resisotrs. Radio engineers usually use 50 ohm coaxial cables and you should not mix up those two different cable types.
Coaxial cable: A cable which has one center conductor, insulation around it and an outer conductor as a shield around the center conductor and it's insulator. This type cable is used to carry high frequency electrical signals like radio waves and high frequency video signals. The coaxial cables used with computer monitors have a characteristic impedance of 75 ohms.
Composite Sync: The horizontal and vertical sync signals are combined into one signal. In this configuration, monitors with BNC connections use four connections: red, green, blue, and sync.
CRT: Short for Cathode Ray Tube.

D

E

ECL: Short for Emitter-Coupled Logic. This type of high speed logic signals are mostly found in super high resolution CAD/CAM computer monocrome displays (for example Sun workstantions).
External Sync: This term means that the sync signals are sent to the monitors "externally", separated from the RGB video signals. This means that there is a separate connector or connectors besides the RGB connectors for the sync signals. Separate horizontal and vertical syncs and Composite Sync belong to this category.

F

Fixed Frequency Monitor: A computer monitor which is designed to operate at only one screen resolutions with strictly fixed horizonal and vertical sync frequencies.

G

H

Horizontal Back Porch: The period of time between the end of the Horizontal Sync pulse and the start of the next horizontal active time is the Horizontal Back Porch.
Horizontal Blank Time: Once the beam has reached the right side of the screen it is quickly moved back to the left side of the screen. As the beam is being directed back, it is always turned off and the time it takes to move back is called the horizontal blank time.
Horizontal Front Porch: The time between the end of the horizontal active time and the start of the horizontal sync pulse is called the Horizontal Front Porch.
Horizontal Sync Width: The amount of time that the horizontal sync pulse is active is called the Horizontal Sync Width.
Horizontal Total Time: The time it takes to make a full horizonal cycle is referred to as the horizontal total time. Adding the Horizontal Active and Horizontal Blank times together equals the Horizontal Total Time.
Horizontal Refresh Rate: The number of horizontal cycles per second is referred to as the Horizontal Refresh Rate and is usually in units of thousands of cycles, Kilohertz. For example, if a monitor horizontally cycles 50,000 times a second, its Horizontal Refresh Rate is 50.0 Kilohertz (written as 50.0 kHz).
Horizontal Sync Pulse: During the horizontal blank time, the monitor receives the horizontal sync pulse which is used for syncronizing the monitor to operate exactly syncronous to the PC graphics card. After receiving the horizontal sync pulse, the monitor returns the beam to the left side of the screen.
Horizontal Total Time: Time it take to make a complete horizonal cycle.If a monitor runs at 50 kHz horizonal refresh rate, each horizontal cycle takes 1/50,000 of second, or 20 microseconds (20 one-millionths of a second).

I

Interlaced Scan: A way to refresh a monitor so that screen is refreshed from up left corner to right bottom corner so that every scanline is scanned in every screen refresh. This method is used in broadcast television to save radio bandwidth, but this is nowadays very rarey used for computer monitors because gives slightly unstable image on computer screen.
Interlacing: Same as Interlaced Scan.
Internal sync: This term describes tells that the sync signals are combined "inside" the video signal instead of sending them separately. For RGB signals the most common "Internal Sync" method is Sync On Green.

J

K

L

M

Multisync Monitor: A monitor which can work with many differenc combinations of different vertical and horizonal sync frequencies and different screen resolutions.

N

O

P

Q

R

RGB: Short for "Red, Green and Blue". Means the primary colors of the computer video system or the video signals and/or connectors associated with them.

S

Separate horizontal and vertical syncs: The horizontal and vertical sync signals are sent as two separate signals. In this configuration, monitors with BNC connections use five connections: red, green, blue, horizontal sync, and vertical sync.
SVGA: Short for SuperVGA. An extension to VGA standard to make the same graphics system to support high resolutions.
Sync On Green: The horizontal and vertical sync signals are combined together with the green signal. In this configuration, monitors with BNC connections use three connections: red, green, and blue.

T

TTL: Short for Transistor-Transistor Logic. In computer video technology this digital 4-5 Vpp signal is used for short cable runs on old video standards like IBM CGA and EGA.

U

V

Vertical Active Time: The total time it takes for all of the horizontal scanlines to be displayed is called the vertical active time.
Vertical Back Porch: The period of time between the end of the Vertical Sync pulse and the start of the next vertical active time is the Vertical Back Porch.
Vertical Blank Time: The time it takes for the beam to be returned to the top is called the vertical blank time.
Vertical Front Porch: The time between the end of the vertical active time and the start of the vertical sync pulse is called the Vertical Front Porch.
Vertical Refresh Rate: The Vertical Refresh Rate of a monitor is simply the number of vertical cycles completed per second, measured in Hertz. For example, if a monitor completes 75 vertical cycles per second, its Vertical Refresh Rate is 75 Hertz (75 Hz).
Vertical Sync Pulse: During the vertical blank time, the monitor receives the vertical sync pulse which is used for syncronizing the monitor to operate exactly syncronous to the PC graphics card. After receiving the vertical sync pulse, the monitor returns the beam to the upper left corner of the screen.
Vertical Total Time: The time it takes for the beam to start at the top of the screen, scan back and forth to the bottom of the screen, and return to the top, is called the vertical total time. Adding the Vertical Active Time to the Vertical Blank Time will equal the Vertical Total Time.
Vertical Sync Width: The amount of time that the vertical sync pulse is active is called the Vertical Sync Width.
VGA: A PC video standard invented by IBM. Maximum resolution supported by original VGA satdard is 640x480.
Vpp: Short for Volts Peak to Peak.