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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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