Glossary Q-T

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Q

Quad

A device that compresses up to four video signals and simultaneously displays the images onto one monitor.

R

Rack Mount

An industrial standard housing 19" wide, its height is measured in units (U’s) of 1.75".

Radio Frequency (R.F.)

Signals with a repetition rate above audible range, but below the frequencies associated with heat and light.

RAID

Redundant Arrays of Independent Disks. The use of two or more disk drives instead of one disk, which provides better disk performance, error recovery, and fault tolerance, and includes interleaved storage techniques and mirroring of important data.

RCA

A common connector plug for standard consumer video and audio equipment. This type of connector plug may also be described as a "phono" plug. RCA jacks are found on all VCRs and televisions equipped to handle a composite and component video.

Ribbon Speaker:

A loudspeaker that consists of a thin, corrugated, metallic ribbon suspended in a magnetic field. The ribbon acts electrically like a low-impedance voice coil and mechanically as a diaphragm.

Remote Playback

A feature of many DVR and NVR recorders. This allows users to play back recorded video over the internet from virtually any computer in the world.

RMS

Root Mean Square or the square root of the arithmetic mean (average) of the square's set of values. A reasonably accurate method of describing an amplifier's power output.

Resolution

A measure of the ability of a camera or television system to reproduce detail. Typically refers to the number of picture elements that can be reproduced with good definition.

Resonant Frequency

The frequency at which any system vibrates naturally when excited by a stimulus. A tuning fork, for example, resonates at a specific frequency when struck.

Reverberation

The reflections of sound within a closed space.

Reverberation Time

The amount of time it takes the reverberation to decay 60 dB from the level of the original sound.

RPTV

Rear-Projection Television

Rs232

A commonly used computer serial interface.

S

S/N Ratio (Signal To Noise Ratio)

Measure of noise levels of a video signal; the higher the number the better.

Saturation (Color)

The vividness of a color. It is directly related to the amplitude of the chrominance signal.

Sampling Frequency

How often a digital sample is taken of an analog wave. The more samples taken, the more accurate the recording will be. You need to sample at a minimum of twice the highest frequency you want to capture. For example, the 44.1-kilohertz sampling rate of a CD cannot record sounds higher than 22.05 kilohertz.

Scan Lines

The lines drawn by an electron gun in a CRT system to make up the picture. Drawn horizontally, from left to right, starting at the top left and working to the bottom right.

SCSI

Small Computer Systems Interface (Pronounced "scuzzy".) A ultra high-speed interface that can connect to computer devices such as a hard drive or CD-Rom. A SCSI channel can connect up to seven devices.

SDTV

Standard Definition Television. Lower resolution subset of the ATSC's DTV system. 480i is typically accepted as an SD signal. Digital broadcasters can offer multiple sub-programs at SDTV quality, as opposed to one or two HD programs. Digital satellite and digital cable often refer to the majority of their programs as SDTV, somewhat erroneously, as neither system has anything to do with DTV, though both, technically, consist of a digital 480i signal.

Sensitivity

A cameras ability to reproduce a given scene with a given amount of light. Usually expressed in foot-candles or lux.

Soft-Dome Tweeter

A tweeter that uses a soft fabric or plastic dome as the radiating diaphragm.

Speaker

A component that converts electrical energy into acoustical energy.

Static IP Address

A Static or Dedicated IP address is a type of account from an ISP where your computer or network is assigned the same constant IP Address at all times. Also see IP Address and Dynamic IP.

Structured Wiring

Also known as Pre-Wire, Structured Wiring commonly refers to the installation of cables and wires in a structure during the building phase. Cables and wires to accommodate CATV, satellite TV, surround sound, telephone, computer networking, video surveillance, security and home automation are installed so when the home is finishes, no cables are visible.

Subwoofer

A speaker designed to reproduce very low bass frequencies, usually those below about 80 Hz.

Switcher

A device used to switch the video signals from two or more cameras on a monitor.

T

Tactile Transducer

A device that turns electrical energy into mechanical energy, usually used to shake the seating in a theater. Effective in providing visceral impact without increasing the system's actual SPL level.

THX

Certification program for home theater equipment. Uses some proprietary features, but mostly assures a base quality level for a given room size. (See THX Select or Ultra.) Is compatible with any and all soundtrack formats. Stands for either Tom Holman's eXperiment, after the engineer who drafted the original standard, or is named after the company's founder George Lucas' first movie, THX 1138. Nobody agrees on which.

THX Select

Certification program for speakers and receivers that assures a base level of quality and performance when played in a room that's between 2,000 and 3,000 cubic feet.

THX Ultra

Certification program for speakers, receivers, and amplifiers that assures a base level of quality and performance when played in a room that's greater than 3,000 cubic feet.

THX Ultra 2

The newest certification from THX, THX Ultra 2 requires amplification for seven channels, boundary compensation for subwoofers, and stricter requirements for amplifiers and speakers than THX Ultra. Dipole speakers are used for the side surround channels. Monopole speakers are used for the surround back channel and are placed next to each other. The Ultra 2 processor accommodates both 5.1 EX/ES soundtracks, as well as multichannel audio recordings by directing ambient sounds to the dipole speakers and discrete effects/sounds to the back channels.

Transducer

Any device that converts one form of energy into another form of energy, specifically when one of the quantities is electrical. Thus, a loudspeaker converts electrical impulses into sound (mechanical impulses), a microphone converts sound into electrical impulses, a solar cell converts light into electricity, etc.

Tuner

See Receiver.

Tweeter

A speaker driver designed to reproduce high frequencies; usually those over approximately 5,000 to 10,000 Hz.

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