CAT-5 (Category 5) This is a copper wire standard used in
digital networks most commonly Ethernet. It uses an RJ-45 plug and 4
pair wire. It is suitable for use in 10 Base-T and 100 Base-T
Radio Consultative Committee) A branch of the International
Telecommunications Union (ITU), a specialized agency of the United
Nations - thus the CCIR is a treaty organization related directly
to the UN. The CCIR is concerned with generating documents dealing
with the preparation, transmission, and reception of all kinds of
information using radio signals, with the term "radio"
being taken in the broadest sense, including television and telephony.
CCITT (International Telephone and Telegraph consultative
Committee) See ITU-T
CD (compact disc) Trademark term
for the Sony-Philips
digital audio optical disc storage system. The system stores
75 minutes (maximum) of digital audio and subcode information, or
other non-audio data, on a 12-centimeter diameter optical disc.
The disc is made of plastic, with a top metallized layer, and is
read by reflected laser light. Variations (such as the 3" disc)
are used for special applications.
CD-R (compact disc-recordable) A compact disc that
is recordable at least once.
CD-ROM (compact disc read-only memory) A method of
storing digitally coded information, such as computer information
or database, on a 12-centimeter diameter optical disc that can be
read but not altered.
CD-V (compact disc video) A system storing five minutes
of analog video and digital audio plus twenty minutes of digital
audio only on a 12-centimeter diameter optical disc, and longer
times on 20- or 30-centimeter diameter optical discs.
center frequency One of the
parameters of a bandpass filter.
The center frequency occurs at the maximum or minimum amplitude
response for Butterworth filters, the most common found in audio
Channel A channel is generally thought of as a separate
path through which signals can flow. (1) In radio and
television, a channel is a separate incoming signal or program
source that a user can select. (2) In the public switched
telephone network (PSTN),
a channel is one of multiple transmission paths within a single link
between network points. For example, the commonly used (in North
system line service provides 24 64
Kbps channels for
digital data transmission. (3) In optical fiber transmission
using dense wavelength-division multiplexing (DWDM),
a channel is a separate wavelength of light within a combined,
multiplexed light stream.
checksum The sum of a group of data items used for error
checking. If the checksum received equals the one sent, all is well.
Otherwise, the receiving equipment requests the data be sent again.
chromatic scale Music.
A scale consisting of 12 semitones.
chrominance The color portion of
the video signal - includes hue and saturation information but not
brightness (see luminance).
clock A timing device that generates the basic periodic
signal used as a source of synchronizing signals in digital
CLR (Common Language Runtime) Microsoft .NET's
equivalent of the Java Virtual machine
CLV (constant linear velocity) A disc rotating at
varying numbers of revolutions per second to maintain a constant
relative velocity between pickup and track across the disc radius.
The CD is a CLV system rotating from 500 rpm (lead-in track) to 200
rpm (lead-out track).
coaxial cable A single copper conductor, surrounded with a
heavy layer of insulation, covered by a surrounding shield and
jacket. A constant-impedance unbalanced transmission line.
A trademark of Peak Audio identifying their licensed
networking technology used for the deterministic and
isochronous transmission of digital audio, video, and control
signals over 10 Mbit and 100 Mbit
Codec (code-decode) A device for converting video
and voice signals from analog to digital for use in digital
transmission schemes, and then converting them back again. Most
codecs employ proprietary coding algorithms for data compression.
compander A contraction of compressor-expander. A term
referring to dynamic range reduction and expansion performed by
first a compressor acting as an encoder,
and second by an expander
acting as the decoder. Normally used in RF wireless applications for
noise reduction or headroom reasons.
Mathematics. Any number of the form a + bj, where
b are real numbers and j is an imaginary number
whose square equals -1; and a represents the real part
(e.g., the resistive effect of a filter, at zero phase angle) and
b represents the imaginary part (e.g., the reactive
effect, at 90 degrees phase angle).
composite video A video signal combining
chrominance, and synchronization data
in a single signal. Often connected between equipment on a
single coax cable using RCA connectors and color-coded yellow.
compression 1. An
increase in density and the resulting decrease in size or magnitude
in a medium. 1.the momentary increase in air pressure, caused by the
passage of a sound wave. 2. The change in the relative
magnitude (peak volume) of and audio signal after processing by a
compressor. 3. A reduction in the total digital size of a signal to
accommodate cost-effective digital transmission or storage. see also
compression ratio A compression ratio usually expressed as
i.e. 5:1, refers to the size of the original data versus the size
after compression by a codec. If the data has been reduced to
one-fifth the original size, the compression ratio is 1:5.
compression wave A wave propagated by means of the
compression of a fluid, such as a sound wave in air.
compressor A signal processing
device used to reduce the
dynamic range of the signal passing through it. For
instance, an input dynamic range of 110 dB might pass through a
compressor and exit with a new dynamic range of 70 dB. This clever
bit of skullduggery is normally done through the use of a VCA
(voltage controlled amplifier), whose gain is a function of a
control voltage applied to it. Thus, the control voltage is made a
function of the input signal's dynamic content.
condenser microphone A
microphone design where a condenser (the original name for
capacitor) is created by stretching a thin diaphragm in front of
a metal disc (the backplate). By positioning the two surfaces
very close together an electrical capacitor is created whose
capacitance varies as a function of the movement of the diaphragm in
response to varying sound pressure. Any change in sound pressure
causes the diaphragm to move, which changes the distance between the
two surfaces. If the capacitor is first given an electrical charge (polarized)
then this movement changes the capacitance, and if the charge is
fixed, then the backplate voltage varies proportionally to the sound
pressure. In order to create the fixed charge, condenser microphones
require external voltage (polarizing voltage) to operate.
This is normally supplied in the form of
phantom power from the microphone preamp or the mixing console.
constant-Q equalizer (also
Term applied to
graphic and rotary equalizers describing bandwidth behavior as a
function of boost/cut levels. Since Q and bandwidth are inverse
sides of the same coin, the terms are fully interchangeable. The
bandwidth remains constant for all boost/cut levels.
critical band Physiology of
Hearing. A range of frequencies that is integrated (summed
together) by the neural system, equivalent to a bandpass filter (auditory
filter) with approximately 10-20% bandwidth (approximately
one-third octave wide). [Although the latest research says
critical bands are more like 1/6-octave above 500 Hz, and about 100
Hz wide below 500 Hz.] The ear can be said to be a series of
overlapping critical bands, each responding to a narrow range of
frequencies. Introduced by Fletcher (1940) to deal with the masking
of a pure-tone by wideband noise.
crossfade Within the audio
industry, a term most often associated with dj mixers. DJ mixers
usually feature a crossfader slide-type potentiometer
control. This control allows the dj to transition from one stereo
program source (located at one travel extreme) to another stereo
program source (located at the other travel extreme). The goal in
crossfader design is to maintain equal loudness (power) in the
system during transition. Contrast with
pan and balance controls.
crossover An electrical circuit (passive
or active) consisting
of a combination of
bandpass filters used to divide the audio frequency spectrum (20
Hz - 20 kHz) into segments suitable for individual loudspeaker use.
Named from the fact that audio reproduction transitions (or
crosses over) from one driver to the next as the signal
increases in frequency. For example, consider a two driver
loudspeaker crossed over at 800 Hz: Here only one driver (the
woofer) works to reproduce everything below 800 Hz, although
both drivers work reproducing the region immediately around 800 Hz
(the crossover region), only the last driver (the tweeter)
works to reproduce everything above 800 Hz. Crossover circuits are
characterized by their type
Linkwitz-Riley being the most popular), and by the steepness of
their roll-off slopes (the rate of attenuation outside their
passbands) as measured in decibels per
interval, such as dB/octave.
crosstalk (magnetic) See:
CRT (Cathode Ray Tube ) Common
electronic "pitcher tube" used in television receivers and computer
Cue 1. A term found throughout various
audio fields meaning to monitor, or listen (via headphones) to a
specific source. In mixers
(particularly dj mixers) the term is used interchangeably with
solo or PFL as found on
recording consoles. 2. A gesture by a conductor signaling the
entrance of a performer or part. 3. A signal, such as a word or an
action, used to prompt another event in a performance, such as an
actor's speech or entrance, a change in lighting, or a sound effect.
current Symbol i, I Electricity. a. A
flow of electric charge. b. The amount of electric charge flowing
past a specified circuit point per unit time, or the rate of flow of
current loop A data transmission scheme that looks for
current flow rather than voltage levels. This systems recognizes no
current flow as a binary zero, and having current flow as a binary
one. Favored for its low sensitivity to cable impedance, and
independence of a common ground reference; hence current loops do
not introduce ground loops. MIDI is
an example of a current loop interconnect system.
cut-only equalizer Term used to
designed only for attenuation. (Also referred to as notch
equalizers, or band-reject equalizers). The flat (0 dB) position
locates all sliders at the top of the front panel. Comprised only of
notch filters (normally spaced at 1/3-octave intervals), all
controls start at 0 dB and reduce the signal on a band-by-band
basis. Proponents of cut-only philosophy argue that boosting runs
the risk of reducing system headroom.
cutoff frequency Filters. The frequency at which
the signal falls off by 3 dB (the half power point) from its
maximum value. Also referred to as the -3 dB points, 3 dB down
points or the corner frequencies.