I

I/O-  Input/Output

IC-  Integrated Circuit

Icon - A symbol that is used to represent a function; i.e. the symbol for painting might look like a paintbrush. Many graphics programs use icons in their menus, rather than words

IEC - International Electrotechnical Commission, charged with the responsibility for developing international standards for audio-visuals. ICIA cooperates with sub-committee SC-60 within IEC

IF - Intermediate frequency a lower radio frequency (typically 10.7MHz) found in the middle stages of a receiver

IM - lntermodulation, frequencies produced by combinations of other frequencies in non-linear devices

Image Buffer - Electronic circuitry which converts 625-line 50Hz video signals to 525-line 60Hz standards and vice versa

Image Orthicon - See TELEVISION CAMERA TUBES

Image Rejection - The ability of a receiver to reject interference from an image frequency (determined by the front end)

Image Scanner, - A device which reads color photos and graphics by scanning reflected light with a CCD sensor May be used with word processors and personal computers.

Impedance - Resistance to the flow of alternating current electricity measured in ohms and abbreviated W or Z.  Low impedance circuits (low W) are 600 ohms or less, and high impedance (hi W)) may be 50K ohms or more

I-Mux - See INVERSE MULTIPLEXER.

In Band - Transmission taking place within allocated bandwidth. For example, a video call with a total of 384Kbps may allocate 32Kbps for audio, leaving 352 for video.

Indirect - Reflected or diffracted

Inductive Loop - A wire loop connected to the output of a tape recorder, phonograph or PA system that produces an electromagnetic field within and adjacent to the loop. A small battery-powered amplifier built into a cordless headphone picks up and amplifies this silent signal to audible levels

Infrared (IR) - Heat rays or waves just beyond (longer than) the visible spectrum; often filtered out to reduce heat on film or slide

Initialize - Prepare for operation. Programs initialize variables by setting their values. Diskettes are initialized by formatting them and, in some cases, installing files. See FOR MAT

Input - The program that enters a unit or system; the jack or receptacle into which a signal is fed

Interactive - Communication in which all participating sites have interactive videoconferencing which permits all sites to see and hear one another.

Intercept (third order) - A measure of the ability of a radio to handle high signal levels without overload or distortion

Intercom - A device or component of a system that permits two-way communication

Interconnects - Cables which are used to connect one product to another such as a VCR to a TV.

Interface - To connect normally incompatible components so that the signal from one is readable by the second. Often transmitting one standard or language to a device which recognizes another, different standard or language

Interference - Energy from an outside source which interferes with a specific signal

Interlace - Scanning system which interleaves the scan lines from odd and even fields to produce a flicker-free image at the rate of 30 fps

Interlacing - Increasing video resolution by doubling the number of horizontal scan lines: NTSC video is interlaced

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Interlock Projector - A special type of projector which can be interconnected with another projector or tape recorder for synchronous running. Used for screening of separate picture and sound tapes or in multiprojection systems. See also DOUBLE BANO PROJECTOR

Internet - The vast collection of inter-connected networks that all use the TCP/IP protocols

Interoperability - The ability of hardware, software, systems, or services to function together without regard to manufacturer or service provider.

Interpolation - In digital video, the creation of new pixels in the image by some method of averaging the values of neighboring pixels. This is necessary when an image is digitally altered, such as when the image is expanded or compressed

INVAR Shadow Mask - A special alloy on shadow mask that produces a brighter, more accurate picture that resists thermal distortion for pure colors under demanding conditions.

Inverse MultipIexer - The creation of a single higher-speed data channel by combining and synchronizing two or more lower-speed channels. (Ascend Communications, 1994)

IPS - Inches Per Second: more properly written in/s. Standard method for measuring the speed of tape movement

IR Filter - See HEAT FILTER

Iris - An adjustable aperture in a lens made of movable meta⁴ parts which change the diameter of the lens opening in order to control the amount of light passing through the lens, Openings are shown in f-stops

ISDN (Integrated Services Digital Network) - A CCITT (now TSS) standard for integrated transmission of voice, video and data. Bandwidths include: Basic Rate lnterface-BRI (144K bps) and Primary Rate-PRI 1.544 and 2.048M bps).

ISDN-1 - A U.S. based variation of the CCITT (TSS) standard. Supported by most U.S. carriers and manufacturers.

ISO (International Standards Organization) - Develops standards such as JPEG and MPEG. Closely allied with the CCITT (TSS).

ITU-T (International Communication Union-Telecommunications) - An international body that sets worldwide telecommunications standards, such as the Px64 standard for videoconferencing.

ITV - Instructional Television, See EDUCATIONAL TELEVISION

IXC (Interexchange Carrier) - Long distance phone company.

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J

Jack - Receptacle for a plug connector for the input or output circuits of an audio or video device. There are several common sizes and formats, including: Standard (1/4’) phone, 0.25’ or 6.35mm; Small phone, 0.206” or 5.23mm; Mini, 0,140’ or 3.6mm; Micro or submini, 0.097” or 2.5mm

Jack Box - A device with one plug and several jacks to permit the connection of a number of units such as headphones to one output jack. Some models are available with variable volume controls.

Jitter - Variations in a waveform due to mechanical disturbances, changes in the characteristics of components, supply voltages, imperfect synchronizing signals, circuits, etc.

Jog/Shuttle Dials - Enables you to move the tape forward and backwards faster and easier, by turning a dial rather than pushing a button.

JPEG (ISO Joint Picture Expert Group) -. Standard for compression of still pictures. Also used for compression of video for desktop multimedia.

K

K - 1024 bytes. The term “K” (Kilo) is used because it is roughly 1,000 bytes. Thus, 64K bytes is actually 65,536 bytes. See also BYTE

Kbps (kilobits per second) - One thousand bits per second. Measure of rate of digital transmission.

Kelvin (K) - An International Standard Unit of color temperature written without the degree symbol

Kerning - Character spacing in which the position of each character is adjusted according to the actual shape and size of the character just before it. Permits some characters to actually be tucked under other characters for a more natural look and for efficient use of space

Keyer - A device to lay computer graphics display over a video display. Usually part of a genlock

Key Frame - An effect stored in memory, similar to a snapshot photograph. Individual frames can be strung together to create an overall key frame effect similar to animation

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Keystoning - The distortion (usually of a wide-top narrow-bottom effect) of a projected image caused by improper projector-to-screen angle

klhz - Kilohertz

Kilohertz (kHz) - 1000 Hertz. A unit of frequency

L

Lag - Ghost image of an object or subject which remains on screen after the image or object is no longer on screen

LAN - Local Area Network; a computer system that allow PC’s, terminals, mainframes, and peripheral devices to interconnect and exchange files

Language Laboratory - See ELECTRONIC LEARNING LABORATORY

Lantern Slide - A once common slide, often glass, 3 1/4 x 4” valuable for projecting maps, charts, schematics, graphs where detail, registration and volume of information are required

LAP - Link Access Protocol

Large Scale Supercomputer - Advanced computers that combine scalar and vector processing techniques to solve complex, computer intensive scientific problems. Supercomputers typically cost from $5 to S20 million

LASER - Light Amplification by Stimulated Emission of Radiation; often used for pointers

Laser Beam Printer - A device which prints information by applying laser light on electrically charged photo-sensitive material. These printers are high quality, fast and have low noise.

Laser Card - A card version of the optical disc, the laser card has an extremely large recording capacity and is more durable than conventional magnetic cards.

Laser Disc - This is a 12” analog movie disc which offers excellent sound and picture and is not subject to wear like video tape.

LATA (Local Access and Transport Area) - One of 161 U.S. geographical areas used to define local telecommunications service (as opposed to inter-LATA or “long distance”).

Lavalier Mike - A small microphone worn on a cord around the neck or clipped to the lapel

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Layering - Combining several video sources into an effect at one time. Each layer of video can be cropped, keyed, sized, positioned or made transparent to expose next lower layer

LCD - Liquid Crystal Display: liquid crystals exist in an intermediate state between liquid and solid, and realign under electrical stimulation. Exceptionally slim and light, they are ideal in word processor, computer and TV displays.

LCD Panel - An LCD device which allows text and graphics information from a personal computer to be displayed onto a large screen or wall using a standard transmissive type of overhead projector as the light source. This type of projection system is economical and lightweight, and allows large groups of people to view the computer display and images at one time. xlarge groups of people to view the computer display and images at one time.

Learning Center - A device, usually a table, into which several people may plug headphones so they may all listen to the same program or, if it has channels, they may listen to one of several programs

LEC - Local Exchange Carrier.

LED - Light Emitting Diode, a semiconductor diode that converts electrical energy into visible electromagnetic radiation. Often used in VCR and other equipment displays

Lens - This is a part that gathers light and focuses it.

Lens Hood - A cylindrical cover attached to the end of a lens to keep ambient light from reaching the lens

Lens Speed - Refers to the ability of a lens to pass light expressed as a ratio: the focal length of the lens divided by the (effective) diameter. A fast lens which passes more light might be rated f/1 .1 or 1.2; a much slower lens which passes less light might be designated F/3.5. The f/number or f# = focal length/aperture

Lenticular - See SCREEN SURFACES

Level - The amplitude or strength of a signal

Light Pen - A mechanical input device which reads coordinates from a display screen or tablet when pointed at a spot on the screen or tablet, The coordinates are then passed to the program for processing. Light pens can be used for drawing, games, and menu selection

Line Feed - An end-of-line character not normally displayed on a computer screen which moves the cursor to the line below, or advances the paper in the printer one line; may be accompanied by a carriage return which moves the cursor to the left of the line. See CARRIAGE RETURN

Line of Best Viewing - Also referred to as ON-AXIS VIEWING. Light from a projector is incident on a screen. Light reflects from the screen such that the angle of reflection equals the angle of incidence. The line of best viewing’ is along the line of reflection

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LLTV - Low Light Television

LO - Local oscillator, in a receiver it is tuned to a frequency which is offset from the operating frequency by an amount equal to the intermediate frequency (IF)

Load - To bring a file or program stored on a disk into the computers memory

Lumen - A measurement of quantity of light taken at the source of the light. Lumens per square foot are footcandles. See also LUX

Luminance (Video) - The relative brightness values of a particular object in a scene. Compare with CHROIMINANCE

Lux - The metric measurement of light quantity. The measurement is taken from the reflection off the object illuminated. One footcandle equals 10.76 lux. A lux equals one LUMEN per square meter