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Reference • Appendix B
Extron • System 5
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Switcher • User’s Manual
Glossary of terms
Following is a list of terms taken from Extron’s Glossary.
AC Reset –
Refers to status that changes when power is removed from a device. Many
electronic devices have live power inside, even after “Power off” has been
initiated from a panel or remote control device. This is not the same as “AC
Reset”, when power is removed at the AC cord.
Attenuation –
The decrease in magnitude (of a signal).
Audio follow –
A term used when audio is tied to other signals, such as video, and they are
switched together. (The opposite of Breakaway)
Balanced Audio –
A method that uses three conductors for one audio signal. They are plus (+),
minus (-) and ground. The ground conductor is strictly for shielding, and does not
carry any signal. Also differential audio.
Bandwidth –
A frequency range, or “band” of frequencies, within which a device operates. In
audio and video, it is the band of frequencies that can pass through a device
without significant loss or distortion. The higher the bandwidth, the sharper the
picture; low bandwidth can cause a “fuzzy” picture.
Breakaway –
The ability to separate signals for the purpose of switching them independently.
For example: an audio and video signal from the same source may be “broken
away” and switched to different destinations. The opposite of the term “follow”.
Buffer –
Generally referred to as a unity gain amplifier used to isolate the signal source
from the load. This is for both digital and analog signals.
Chroma –
The color information (hue and saturation), independent of luma intensity. Black,
gray, and white objects do not have chroma characteristics.
Chroma Signal –
Part of a television signal containing the color information. Abbreviated as “C”.
Clip, Clipping –
The level at which a signal excursion begins to exceed limits of the circuit and
flattens out, distorting the signal. When setting audio attenuation, the clip level
can be defined as a level short of the distortion point, thus allowing “headroom”
and maintaining the signal’s fidelity.
Composite Sync –
A signal consisting of horizontal sync pulses, vertical sync pulses, and equalizing
pulses only, with no signal reference level. Also referred to as RGBS.
Composite Video –
A combined signal which includes luma black and white, chroma (color), blanking
Differential Audio –
See Balanced Audio.
DLP –
Digital Light Processing – Also DMD (Digital Micro-mirror Device). Uses an array
of mirrors that move independently, reflecting light to compose the picture.
Gain –
A term used to denote an increase in signal power or voltage produced by an
amplifier in transmitting a signal from one point to another. The amount of gain is
usually expressed in decibels above a reference level. Opposite of Attenuation.
Headroom –
The margin between a nominal operating signal level and peak clipping
(distortion) level. See Clipping.
High Impedance
(Hi Z/High Z) – This is typically 10k ohms or greater. In video, when the signal is
not terminated locally, there may be a switch for Hi Z or some termination value
(75 ohms). Hi Z is used if termination is provided by another device.
IR Learning –
The ability of a device to receive and store infrared commands for other devices,
such as the projector. With Extron’s System 5, each command is assigned to a
system operation (such as selecting an input). When an operation is executed,
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