| A |
| AC |
Alternating Current - Flow of Electrons that changes direction alternatively. |
| A/D |
Analogue to Digital |
| ADA |
Analogue Distribution Amplifier |
| Adapter |
The shared component in a system that handles only host interface and communication connection functions; also, an interface between two sources. |
| Additive Color Process |
(also called RGB) - A colour generation process used in video that combines Red, Green and Blue to make all colours. All three colours (red, green and blue) at 720 make white on a video screen, absence of all three makes black. See Subtractive Colour (CMYK) |
| Amorphous |
Without definite form of shape not crystallised. |
| AMPS |
A unit of measure of current |
| Analog |
A signal of continuously varying level. Standard audio and video signals are analogue. This signal has an infinite number of levels between its highest and lowest value. (Not represented by bits, such as with digital.) |
| ANSI |
American National Standards Institute. |
| ANSCII |
American Standard code for Information Interchange. The standard audio code consisting of 7-bit coded characters (8 bits including parity check), utilised to exchange information between data processing systems, data communication systems and associated equipment. The ASCII contains control characters and graphic characters. |
| Aspect Ratio |
Horizontal dimensions of a picture expressed relative to the vertical dimensions. The aspects ratio of all broadcast composite video systems is 54 units wide by 3 units high. |
| Attenuation |
The decrease in magnitude of a signal |
| Autosizing |
Automatic picture sizing adjustment to compensate for different display modes, then enabling the display to centre the picture and fill the screen |
| B |
| Balanced Audio |
A method that uses three conductors to one audio signal. They are plus (+), minus (-) and ground. The ground conductor is strictly for shielding, and does not carry any signal. See also Differential audio. |
| Bandwidth |
A frequency range, or "band" of frequencies, within which a devices operates. In audio and video, it is the band of frequencies that can pass though a device without significant loss or distortion. The higher the bandwidth, the sharper the picture; low band width can cause a "fuzzy" picture. |
| Black & White |
Monochrome or luminance information. Monochrome means one colour. In the colour television system, the black and white portion of the picture has to be one "one"; grey, D6500, 6500k as defined by x and y values in the 1938 CIE colour coordination system. |
| Blanking |
The turning off of the electron beam that scans the image onto the screen. When the beam completes a scan line it must return (retrace) back to the left. During this time, the beam must be turned off (horizontal blanking). Similarly when the last line has been scanned at the bottom of the screen, the beam must return to the upper left. This requires vertical blanking. |
| Blue Enhancement |
Mixes the right amount of blue information with the green signal for displaying text in a more readable "aqua" colour. This colour mixing effects all blue colours on the display screen (only used for TTL signals) |
| BNC |
It is a cylindrical bayonet connector which operates with a twist-locking motion. Two curved grooves in the collar of the male connector are aligned with two projections on the outside of the female collar. This allows the connector to be locked in place without the need of tools. |
| BOW |
The curving of scan lines in the centre of the image. |
| Brightness Ratio |
The difference between the brightest and darkest object in a picture. Too much difference can cause unacceptable..... |
| Brightness Signal |
Same as the luminance (Y); a signal which carries information about the amount of light at each point in the image. |
| Buffer |
Generally referred to as a unity gain amplifier used to isolate the source from the load. This is for both digital and analogue signals. |
| Burn-In |
In video display, a term to describe when an image has been displaying too long, resulting in a permanent image being "burned in" to the screen phosphor. |
| C |
| Cache |
A small amount of relatively high-speed storage, which is used as an intermediary between the data user and a larger, slower storage device (the backing store). |
| Capacitance |
A measure of the ability of an item to store an electrical charge. |
| CD-I |
Compact Disc Interactive - A format that provides audio, digital data, still graphics and limited motion. |
| CD-ROM |
Compact Disc Read Only memory. A 4.75 inch laser-encoded optical memory storage medium with the same constant linear velocity (CVL) spiral format as compact audio discs and some videodics. |
| CD-ROM XA |
Compact Disc Read only Memory Extended Architecture. An extension of the CD-Rom standard billed as a hybrid CD-Rom and CD-1, and promoted by Sony and Microsoft. The extension adds ADPCM audio to permit the interleaving of sound and video data to animation, with sound synchronisation. |
| Chroma |
The characteristics of colour information, independent of luminance and intensity. Hue and Saturation are qualities of chroma. Black, grey and white objects do not have chroma characteristics. |
| Chromiance Signal |
Part of a colour television signal containing the colour information. Abbreviated by "C". |
| Coaxial Cable |
A two-conductor wire in which one conductor completely wraps the other with the two separated by insulation. Constant impedance transmission cable. |
| Colour Burst |
In colour systems, a burst of sub-carrier frequency located on the back porch of the composite video signal. This serves as a colour synchronising signal to establish a frequency and phase reference for the chrominance signal. |
| Colour Red, Green Blue and Composite Sync outputs |
Provides analogue Red, Green and Blue level. 7 Volt P-P video output signals and negative going 4 volts P-P, non-terminated and 2.3 volts P-P terminated TTL level composite sync output, matching the input standards of most data monitors and projectors. With sync on the green channel, some large screen data monitors and projectors may display a greenish tint, as well as pulling to the right at the top or bottom. Stripping sync from the green video and using the separate sync output on those interfaces solves these problems. Sync can be added to the green channel by setting the "Sync on Green" switch. |
| Comb filter |
So called for its frequency response, the comb filter providers a better method of separating Y and C than a chroma bandpass or chroma trap. Therefore produces better quality video. (Less crawling, or "zipper" artefacts). |
| Component |
(Video Signal) - The fundamental electronic signal for producing video images. Three of these signals are needed for colour video and the term component is used to indicate one considered alone. The signals may be in digital or analogue form. They may be in the combination of Red, Green and Blue or they may be in some other form such as luminance, R-Y and B-Y. In general the RGB signals can be arithmetically combined into any three components necessary to make the colour picture . |
| Component Video |
Our colour television systems starts with three channels of information: Red, Green and Blue (RGB). In the process of translating these channels to a single composite video signal they are other converted to Y, R-Y and B-Y. Both 3 channel systems, RGB and Y, R-Y, B-Y are component video signals. They are the components that eventually make up the composite video signal. Much higher programme production quality is possible if the elements are assembled in the component domain. |
| Composite Sync |
A signal of horizontal sync pulses, vertical sync pulses and equalising pulses only, with no signal reference level. |
| Composite Video |
A mixed signal comprised of the luminance black and white, chrominance (colour), blanking pulses, sync pulses and colour burst. |
| Contrast |
The range of light and dark values in a picture or the ratio between the minimum and maximum brightness values. Low contrast is shown mainly in shades of grey, while high contrast is shown as blacks and white with very little grey. It is also the TV monitors adjustment which increases and decreases the level of contrast of a televised picture. |
| Contrast Ratio |
This is the ratio of highlight output level divided by the low light output level. In theory, the contrast ratio of the television system should be at least 100:1, if not 300:1. In reality there are several limitations. In the CRT itself, light from the adjacent elements contaminate the light emitted from the CRT. Well controlled viewing conditions should yield a practical contrast ratio of 30:1 to 50:1. |
| Convergance |
The alignment of the Red, Green and Blue video on a projector display. |
| CRT |
(Cathode Ray Tube) - A vacuum tube that produces light when energised by the electron beam generated inside the tube. A CRT has a heater element, cathode, and grids in the neck of the tube, making up the "gun". An electron beam is produced by the gun and is accelerated toward the front of the display, or screen surface of the tube. The display contains phosphors that light up when hit by the electron beam,. The CRT is more commonly known as a picture tube. |
| D |
| D/A |
Digital to Analogue |
| DAT |
Digital Audio Tape - A method of recording information on tape at a high density and high quality. The method uses a rotating head, similar to that used in video tape recording. |
| DC |
Direct current - The flow of electrons in one direction. |
| Decoder |
A device used to separate the RGBS (Red, Green, Blue and Sync). |
| Digitisation |
The transformation of an analogue signal into digital information. |
| DIP Switches |
Tiny switches that are used to change settings on printers, computers, interfaces, switchers, modems etc. They are designed to fit in a input source on a circuit board. |
| Distribution Amplifier |
A device that allows connection of one input source to multiple output sources such as monitors or projectors. |
| Dot Pitch |
The distance between the sets hols or slots (Trinitron System) for the colour on the adjacent line of CRT monitor shadow mask. A smaller dot pitch allows for more potential dots to be displayed, thus achieving better resolution. |
| H |
| HDTV |
High Definition Television - The term describes several advanced standards proposed to allow high-resolution TV to be achieved in the home. |
| Hertz |
Hz - A measure of frequency in cycles per second. |
| Horizontal Blanking |
(Retrace) - The process of bringing the electron beam in a CRT back to the left side of the screen after a left to right line has been traced on the screen. The beam is shut off, blanked, during the period of retrace. About 83% of the total horizontal line time is spent writing the line. The remaining 17% is spent bringing the beam back to the left side; retrace before starting the next line. |
| Horizontal Rate |
Frequency - The number of complete horizontal lines, including trace and retrace, scanned per second. Typically shown as a measure of KHz. |
| Horizontal Resolution |
Smallest increment of a television picture that can be discerned. in the horizontal plane. This increment is dependant upon the video bandwidth and is measured in frequency. Determines the number of lines it takes to scan an image on the screen. |
| HUE |
Tint Control - Red, Yellow, Blue etc are hues of colour or types of colour. Hue is the parameter of colour that allows us to distinguish between colours. |
| HUM |
Unwanted coupling of a power sine wave into other electrical signals. In audio a "hum" can be heard, in video, waves or bars can been seen in the picture. |
| Hz (Hertz) |
A measure of frequency in cycles per second. |
| P |
| PAL |
(Phase Alternate Line) - The phase of the colour carrier is alternated from line to line. It takes four full fields, two full pictures for the colour to horizontal phase relationship to return to the reference point. This alternation helps cancel out phase errors, the reason the hue control is not needed on PAL TV sets. PAL in its forms is used extensively in Western Europe. |
| Pentium |
Intel's i586i CPU chip - competitive to RISC technology. |
| Peripheral |
Any device that a CPU communicates with, such as a printer, mouse, external disc drive, interface etc. |
| PGA |
Professional Graphics Adapter. Resolution 640 x 400. |
| Pixel |
A definable location on a display screen that consists of multiple or single triad of dots (red, green and blue). A computer picture is typically composed of a rectangular array of pixels (i.e. 400 x 450). The resolution of a picture is expressed by the number of pixels in the display. For example, a picture with 560 x 720 pixels is much sharper than a picture with 256 x 400 pixels. |
| Port |
A connector on a computer or peripheral that allows it to be connected to something else. Typical ports are to be found on a computer include serial, parallel, disk drive, video and external keyboard. |
| Primary Colours |
Colors, usually three, which are combined to produce the full range of other colours within the limits of a system. All non-primary colours are mixtures of two or more of the primary colours. In television, the primary colours are specific sets of red, green and blue. |
| R |
| Raster |
The illuminated face of a video screen without the video information present. the pattern of scan lines on which a picture is produced. |
| Resolution |
The density of lines or dots that make up the image.
Resolution determines the detail and quality in the image
a) A measure of the ability of a camera or television system to reproduce details.
b) In video, generally called horizontal resolution. It can be evaluated by establishing the limit to which lines can be distinguished on a test pattern. A larger resolution value means a broader frequency band of the video signal.
c) A measure of the greatest amount of details that can be seen in an image. Often incorrectly expressed as a number of pixels on a given line; more correctly it is the bandwidth. |
| RGB |
(Red, Green and Blue) - The basic components of the color television system. They are also the primary colors of light. Also called the "Additive Color Process". |
| RGB Video |
A form of color video signal (red, green and blue) distinctly different from the composite color video used in standard television sets. RGB can be displayed only on a color monitor that has a separate electron gun for each of these primary colors. Some color television sets use only one gun. RGB monitors are noted for their crisp, bright and high resolution. |
| Retrace |
During the scanning of a picture onto a screen, scan lines are produced from left to right. Before scanning the electron beam gets back to the left side of the screen. This is called "Retrace". The beam must be turned off (blanked) during the retrace time. See Horizontal Blanking and Vertical Blanking. |
| RS232 |
An Electronic Industries Association (EIA) serial digit interface standard specifying the electrical and mechanical characteristics of the communication path between two devices. This standard is used for relatively short range communications and does not specify balanced control lines. |
| RS422 |
An EIA serial digital interface standard which specifies the electrical characteristics of balanced voltage digital interface circuits. This standard is usable over longer distances than RS232C. Although originally designed for use with 9-pin and 37-pin D-type connectors. It is often used with others, including 25-pin D-types. It is also used as a serial port standard for Macintosh computers. this signal governs the asynchronous transmission of computer data at speeds of up to 920,000 per second. |
| S |
| Saturation |
The intensity of the colour is called saturation. For example, a lightly saturated red looks pink. Fully saturated red is like the red of a crayon. On a display device, it can be adjusted with the colour control. Not to be confused with the brightness, saturation is the amount of pigment in a colour, and not the intensity. Low saturation is like adding white to the colour. |
| Scan-Doubling |
The process of eliminating the visible video scan lines by doubling them and filling in the blank lines. |
| SCSI |
(Small Computer System Interface) - An industry standard input/output for peripheral computer devices, such as hard disks and CD-Rom drives. |
| Scanning |
The process of moving the electron beam across the surface of the video screen, or CRT. |
| SECAM |
(System En Coleur Avec Memorie) - Translated as "Sequential Colour with Memory". A composite colour transmission. One of the colour difference signals is transmitted on one line and the second is transmitted on the second line. Memory is required to obtain both colour difference signals for colour decoding. This system is used in France, Africa, Asia and many Eastern European countries. |
| Serial Port |
An output on the computer that allows it to communicate with other devices in a serial fashion - data bits flowing on a single pair of wires. The serial port is most often used with RS-232C protocol. |
| Sub-Carrier |
The modulation sidebands of the colour sub-carrier containing the R-Y and B-Y information. |
| Super VGA |
A term used to denote higher than VGA (640x480) resolution. Most super VGA computers/cards output resolutions up to 180x1024 and 16 million colours. |
| Switcher |
Term often used to describe a special effects generator; a unit which allows the operator to switch between video / audio signals. Switchers are often used in industrial applications to switch between video cameras monitoring certain areas for display on a monitor, or system of display devices. These kinds of switchers do not have sync generators. |
| SYNC |
In video, a means of synchronising signals with timing pulses to ensure that each step in a process occurs at exactly the right time. For example, Horizontal Sync determines exactly when to being each horizontal line (sweep) of the electron beam. Vertical Sync determines when to bring the electron beam to the top-left of the screen to start a new field. There are many other types of sync in a video system. (Also called Sync Signal or Sync Pulse). |
| S-VHS |
A high band video recording process "for VHS that increases the picture quality and resolution capability. See S-Video. |
| S-VIDEO |
The composite video signal is separated into the Luminance (Y) and the Chrominance (C). |
| T |
| Termination |
A load at the end of a cable or signal line used to match the impedance of the equipment being used. Usually a close-tolerance resistor, a terminator is often mounted on its own connector, making it easy to install. The resistor absorbs signal energy to prohibit signal reflections back towards the source. This causes the source equipment to operate as if the line is connected to equipment of equal impedance. |
| Terminator |
A device, usually having its own connector, that provides termination for a signal line, or several signal lines, at the end of a cable. |
| Time Code |
A digital of binary code used to label each frame of a video signal. This is very useful for editing video since the time code is in the form of hours, minutes, seconds and frames. |
| TINT |
See Hue |
| TTL |
(Transistor to Transistor Logic) - Digital type signal, usually 4-5 volts peak to peak. Distance limitation is 6-10 feet. Signal splitting is acceptable. TTL signal are either "ON" or "OFF" and are characteristics of low resolution computers. |
| V |
| VESA |
Video Electronics Standards Association - A non-profit member organisation dedicated to facilitating and promoting personal computer graphics through improved graphics standards for the benefit of the end-user. |
| Vertical Blanking |
(Retrace) - The turning off of the scanning electron beam in a CRT during the time the beam must return from the bottom of the screen to the top. Vertical blanking occurs between writing each field of a picture. If vertical blanking does not occur, a diagonal "retrace" line will display from lower right to upper left of the screen. See also Retrace. |
| VGA |
Video Graphics Array. Introduced by IBM in 1987, VGA is an analogue signal with TTL level separate horizontal and vertical sync. The video outputs to a 15-pin, HD connector and has a horizontal scan frequency of 31.5kHz and vertical frequency of 70-Hz (mode 1,2) and 60 Hz (mode 3). The signal is non-interlaced in modes 1,2 and 3 and interlaced when using the 8514/A card (35.5 kHz, 86Hz) in mode 4. It has a pixel by line resolution of 640x480 with a colour patette of 16/256,000 |
VDA
Video Distribution Amplifier |
An amplifier for strengthening the video signal so that it can be supplied to a number of video monitors (etc) at the same time. |