Post-war and on to 1975 (continued)

Major changes took place in international communications also and at the Empire Telecommunications Conference held in London in 1945, agreement was reached for the amalgamation of British Commonwealth cable and radio services and for their transfer to public ownership. The Overseas Telecommunications Commission (Australia) was formed by Act of Parliament on August 7, 1946, its responsibility being the maintenance and operation of Australia's overseas telecommunications services as well as communications with ships. At that time the acquisition began of the communications assets of AWA, which had operated the overseas wireless services, and of Cable and Wireless overseas telegraph facilities, with C&W retaining ownership of the cables themselves, while the cable stations in Australia and Norfolk Island came under the ownership of OTC. When the sovereignty of Cocos-Keeling Islands transferred from the United Kingdom to Australia in November 1955, the C&W cable station was sold to OTC.

Telegraph cable technology, which had given the world, and Australia, its first international communications system, was by then being supplanted by later technologies. Wireless telegraphy had developed strongly, providing voice communications as well as telegraph, while developments in the nineteen fifties were to result in new types of cable, multi-channel telephone cable, playing a major role in international communications. In the meantime, rapidly growing requirements had to be met by upgrading HF radio installations and by further exploiting the existing telegraph cables.

One way in which this was achieved was by installing a submerged repeater in a Cottesloe (West Australia) to Cocos Island cable. Perth was Australia's western gateway for cable traffic to Singapore and to London via Africa, with two cables connecting Cottesloe with Cocos Island, the 1901 slow cable (Cosclo 1) and the 1926 (Cosclo 2) which provided considerably faster transmission because of its loaded construction. The inclusion of the repeater greatly increased the speed of transmission on Cosclo I.[33]

When Melbourne was selected as the host city for the Games of the XVI Olympiad, it became necessary to accelerate a series of projects which would otherwise have been spread over a number of years, to achieve capacity for an estimated threefold increase in the volume of international traffic to be generated by the Games. This increase was achieved by:

1. installation of new telegraph transmitters, using Frequency Shift Keying (FSK) and Independent Sideband (ISB) Transmission


2. upgrading of existing telegraph transmitters to FSK and ISB working


3. use of Time Division Multiplex (TDM) with Automatic Repeat Request (ARQ) on radio derived circuits to provide automatic error correction for teleprinter channels


4. use of submarine telegraph cable derived circuits for teleprinter operation


5. conversion of radiotelephone transmitters on independent sideband (ISB) operation for voice and phototelegram


6. use of transmitters owned by the Royal Australian Army and Royal Australian Navy

The writing of specifications for high performance transmitting and receiving equipment was carried out by OTC engineers, the transmitter design in particular making demands upon the current technology. The transmitters were of 10 and 30 kW, auto tuned over the frequency range of 3 to 30 MHz, linear for ISB operation and had tight frequency tolerances. The contractor for this work was AWA, who successfully completed manufacture in time for the Olympics, using Marconi technology modified to meet Australian requirements. The design of the advanced antenna systems was carried out by OTC and consisted of rhombics in a circular pattern for maximum flexibility in geographic and frequency coverage. Rhombics were state-of-the-art antennae, characterised by high directive and gain and moderate band-width and represented a considerable overall improvement over the Franklin antennas in use in Victoria. The basis for the design of the rhombics was primarily the pioneering work of Dr. Wilbur Christiansen and W. Jenvey of AWA Laboratories (1946), Jenvey later becoming Chief Engineer of OTC.

Australian Academy of Technological Sciences and Engineering