Glossary E-H

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EDTV: Extended Definition Television

This CEA-adopted term (though originally mentioned in an April '99 HT article by Mike Wood and Mike McGann) is defined as those products that can display DTV images as 480p or higher.


A device that superimposes electronic signal information on other electronic signals.


The rearrangement of the bit stream of a previously digitally encoded signal in a systematic fashion to make the information unrecognizable until restored on receipt of the necessary authorization key.


A component designed to alter the frequency balance of an audio signal. Equalizers may be graphic, parametric, or a combination of both.


A local area network used for connecting computers, printers, workstations, terminals, etc. within the same building.


Fiber Optic Cable

Glass, plastic, or hybrid fiber cable that transmits digital signals as light pulses.

Field Of View

The maximum viewed image (area covered) a lens "sees." The horizontal or vertical scene size at a given distance from the camera.

Focal Length

The distance (in millimeters) from the lens to the surface of the image sensor. The shorter the distance, the wider the view; the longer the distance, the narrower (telephoto) the view.

Foot Candle (FC)

A measurement of light. 1 lumen per square foot.


The number of cycles (vibrations) per second. In audio, audible frequencies commonly range from 20 to 20,000 cycles per second (Hz). In video, frequency is used to define the image resolution. Low-frequency video images depict large objects or images. Higher frequencies depict smaller objects (finer details).


A speaker designed to reproduce the full range (20 Hz to 20 kHz) of audio frequencies.


A term used to indicate the speed of a lens. The smaller the f-number, the greater is the amount of light passing through the lens



Any increase or decrease in strength of an electrical signal. Gain is measured in terms of decibels or number of times of magnification.


A shadowy or weak image in the received picture, offset to either the right or to the left of the primary image.

Gray Scale

The number of variations from white to gray to black.

Graphic Equalizer:

A type of equalizer with sliding controls that create a pattern representing a graph of the frequency-response changes. Raising sliders boosts the affected frequencies; lowering sliders cuts (attenuates) the affected frequencies.


An electrical connection point which provides a common electrical reference for all energized devices. A ground wire may or may not be used for operational current.

Ground Loop

Effects video pictures in the form of a black shadow bar across the screen or as tearing in the top corner of a picture. Caused by different earth potentials in a system.


HDDTV - High definition digital television

The upcoming standard of broadcast television with extremely high resolution and aspect ratio of 16:9. It is advancement from the analog high definition, already used experimentally in Japan and Europe. The picture resolution is nearly 2000×1000 pixels, and uses the MPEG-2 standard.


HDTV connection format using a DVI interface that transfers uncompressed digital video with HDCP copy protection and multichannel audio.

HDTV - High definition television

The high-resolution subset of our DTV system. The FCC has no official definition for HDTV. The ATSC defines HDTV as a 16:9 image with twice the horizontal and vertical resolution of our existing system, accompanied by 5.1 channels of Dolby Digital audio. The CEA defines HDTV as an image with 720 progressive or 1080 interlaced active (top to bottom) scan lines. 1280:720p and 1920:1080i are typically accepted as high-definition scan rates.

Head End

Term used to describe a central location for all signal distribution equipment.

Home Theater in a Box

A complete home theater system in one box (or at least sold together as a package). Consists of five or more speakers, a subwoofer, and a receiver. May also include a DVD player.

Horizontal Resolution

The maximum number of individual picture elements that can be distinguished in a single scanning line.


A type of speaker that looks like a horn. These speakers have small drivers and very large mouths; the horn shape serves to transform the small radiating area of the driver into the much larger radiating area of the mouth of the horn.

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