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Audio
channel: a communications channel capable of carrying
signals audible to the human ear. Such signals are voice,
facsimile and some low speed data communications.
Audio mixer: a device allowing multiple audio
sources to be individually controlled and added together
(or mixed) to produce one or more audio outputs suitable
for broadcast.
Balanced line input: an input to an audio mixer
where the signal provided by the input device is not
relative to ground. Many microphones provide this type
of audio input.
Broadcast or program line: a communication circuit used
to transmit program content from one location to another.
Codec (Coder/decoder): a Codec is a piece of
communications equipment that performs the dual functions
of encoding a signal prior to transmission over a channel
and decoding a signal received from the channel.
DAT: Digital audio tape (DAT) is a format for
recording sound digitally onto magnetic tape that was
developed by Sony and Philips in the mid 1980s.
Dual tone multi-frequency (DTMF): a widely used
telephony signalling scheme that allows the transmission
of data across an audio channel. The scheme derives
its name because each data symbol transmitted is physically
encoded as a pair of audio frequencies.
Frequency modulation (FM): a modulation scheme
where the frequency of the broadcast signal is controlled
by the modulating audio signal. This scheme is less
susceptible to noise interference than amplitude modulation
(AM). For this reason, FM is used widely for high quality
audio transmission.
Integrated services digital network (ISDN): a set
of protocol and interface standards produced by the
CCITT, an international standards body. These standards
describe methods for the integrated transmission of
voice, fax, video and data.
ISDN Microlink®: a Telstra product providing
ISDN services. Aimed at the residential or low capacity
user, it offers up to two 64kbps (64000 bits per second)
communications links. This product is now know under
the product name of Telstra OnRamp®.
Kilohertz (KHz): a unit of frequency measurement
equal to one thousand cycles per second.
Landline: a term used to describe a communications
channel that is not carried via satellite.
Latching relay: an electronic component that
acts as a mechanical switch, where the state of the
switch is determined by the state of a control signal.
MiniDisc: a high capacity digital storage medium
for audio content. This format utilises magnetic technology
to store data and is designed for ease of recording
straight to disc.
RCA: RCA plugs and jacks are a commonly used
style of connector found on audio equipment such as
hi-fi and consumer electronics. RCA stands for Radio
Corporation of America, which established its use as
a standard connector type.
Rebroadcast: the process where a radio broadcast
signal is received at one frequency, amplified and then
retransmitted at another frequency to multiple receivers.
Satellite uplink equipment: the electronic equipment,
located at an earth station, that performs the tasks
required to transmit a radio signal from the earth station
to a satellite.
Talkback: a facility allowing a voice signal
to be transmitted in the opposite direction to the broadcast
content signal. Such a facility may be used in a recording
studio where the sound engineer can use the talkback
channel to direct the performers.
Terminal adaptor: a piece of communications equipment
that acts as the interface to ISDN services in the customer's
premises. This device is where a customer will connect
their communications equipment to the service.
Transponder: the radio equipment that allows
a satellite to receive a signal from an earth station
at one frequency, then amplify and retransmit the signal
back to earth at another frequency. A satellite typically
carries a number of transponders each dedicated to a
particular type of service.
TRI: is short for the McCubbin Electronics TRI-MM
Telephone Hybrid unit. This unit converts the two-wire
telephone connection provided by the Telstra network
into a seperate two-wire transmit and a two-wire receive
connection suitable for use within the studio.
Unbalanced line input: an input to an audio mixer
where the signal provided by the input device is relative
to ground. Inputs from musical instruments such as guitars
are of this type.
Ultra high frequency (UHF): this frequency range
occupies a band in the radio frequency spectrum between
300 MHz (300 MegaHertz is equal to 300 000 000 cycles
per second) and 3 GHz (3 GigaHertz is equal to 3 000
000 000 cycles per second). This band is used for UHF
TV broadcast, some radar installations, mobile phones,
two way radios and many other services.
64Kb semi-permanent: a digital communications
channel providing 64Kb (64 000 bits per second) transmission
capacity in both directions. The channel is established
between two designated sites and is maintained over
a long period of time, hence the name semi-permanent.
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