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Establishment of the BRACS network

As far back as late 1992, there were discussions on how to set up links to Alice Springs to take advantage of the offer by IMPARJA for TEABBA to make use of a spare audio channel on their transponder (OPTUS B1).

To get the program to IMPARJA in Alice Springs, two options were looked at by management:

  • a program line or
  • an ISDN circuit.

As TEABBA was operating on a limited budget, both proposals were considered too expensive at the time, consequently the network idea was put on hold until more funds could be obtained to purchase the equipment needed.

The Board were still keen to get a network operating initially from the Darwin studio, then later linking the community stations (BRACS) into the network.

Revisiting the options available to them ISDN was again ruled as being too expensive; TEABBA did not have the capital required to purchase the ISDN interface units. TEABBA proceeded with the only other option available - a 10khz mono landline between Darwin and the IMPARJA uplink point at Alice Springs.

The connection was finally made and coincided with the move to the new Darwin studios. The first broadcast into the TEABBA satellite radio network took place on the 7th July 1994.

With the main connection for the network up and running, the next problem was how to fill the channel with program. TEABBA could only provide limited output due to low staff numbers. Broadcasting was limited to morning programs and community stations were not as yet connected so the other alternative was to use program from CAAMA radio studios and feed it into the satellite channel when TEABBA was unable to provide program.

Remote switching
To make this connection, remote switching at the IMPARJA uplink feed point had to be achieved from the Darwin studio. Evan Wyatt designed and constructed a simple dual tone multi-frequency (DTMF) transmitter and receiving unit especially for this purpose. The principle was simple, when CAAMA program was required to feed into the satellite channel:

  • the Darwin operator would press the changeover button
  • the studio output program was cut
  • DTMF tones were then sent down the program line, picked up by the receiving unit at IMPARJA
  • the tones were decoded and the appropriate latching relay would be activated to direct either TEABBA or CAAMA program into the satellite channel.

The inconvenience of having the tones broadcast (1/2 second) far outweighed the cost of having a separate control line from Darwin to Alice Springs.

When these decisions were made, there were plans to revisit the shortcomings in the system. When more funds became available to purchase ISDN equipment, and when a higher level of program output from the Darwin studio was achieved, the need for remote switching and supplementing the program with that from CAAMA would be eliminated.

Remote control switching diagram
Remote control switching diagram. Courtesy: TEABBA.

Studio program links
The next step in setting up the network was to connect the community radio stations into the network. After initial discussions with Telstra it became obvious that 10khz or 3khz dedicated program lines would not be available in most communities, due to capacity limitations of the existing communications network. It seems Telstra had not envisaged there would be a demand for permanent program lines out of a community. In fact quite the opposite looks set to happen, with the emergence of more community based broadcasters recognising the need to network.

This landline approach was abandoned, as the closest TEABBA could get to a community with a program line was to a major centre such as Gove in the east Arnhem Land region, the annual costs were in the vicinity of $20 000.

TEABBA was confronted with three options:

  • do nothing and wait for line capacity in communities to be increased
  • wait for new technology to come on the market that could improve the quality of existing links
  • keep the momentum of enthusiasm running and use dial up telephone lines as program lines with telephone talkback units as the temporary program line interfaces, this arrangement would at least provide 3khz program lines, which was better than nothing.

TEABBA decided to go with the third option.

Two units were purchased, the TRI-MM Telephone Hybrid unit (TRI) was installed at the Darwin studio end and the smaller Reporters Telephone Link (RTL) was installed at Galiwinku community radio station.

*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 separate two-wire transmit, and a two-wire receive connection, suitable for use within the studio.

The operation was simple:

  • a telephone handset was connected through the telephone units at both ends
  • Darwin studio would call the community station when contact was made
  • both ends would then press the transfer button on their respective interface units
  • the handpiece connection would drop out and the result is a 3khz broadcast line.
    The idea worked well and is still in use today, with not one single complaint of the program quality.
Temporary program line interface
Temporary program line interface. Photo: Evan Wyatt. Courtesy: TEABBA

First network broadcast
After these initial tests proved that the system could work, arrangements were made with Galiwinku community BRACS station to commence broadcasting through the network on 7th July 1994. The broadcaster was Frank Djirrimbilpilwuy, significant in that he was the founding chairman of TEABBA.

Equipment used for this initial broadcast was not the sort of stuff big networks are made from, it comprised:

  • a simple 4 channel mini audio mixer
  • a hand held microphone and two tape decks.

The output was fed into the telephone interface for transmission over the satellite network via the Darwin studio.

Typical interface connections and equipment
Typical interface connections and equipment. Courtesy: TEABBA


1. Draw a flowchart to illustrate the remote switching using DTMF designed by Evan Wyatt.
2. Draw a diagram to illustrate the operation of dial up telephone links as program lines.


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