Chapter 8
I Part 1: Communications
i Before the Telegraph
ii Electrical Communication Before Federation
iii Federation to the End of the Second World War
iv Post-war and on to 1975
v 1975 ONWARDS
II Epilogue
III Part 2: Early Australian Computers And Computing
IV Acknowledgements
References
Index
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1975 ONWARDS (continued)
With rapidly increasing demand for communication channels and the growing cost effectiveness of optical fibre systems, a decision was taken to install a Sydney-Melbourne cable for commissioning in 1988, basically comprised of 30 fibres but increasing to 42 fibres over some sections and to be equipped to provide 140 and 565 Mbit/sec streams. Other cables will follow within a few years as sections of a national network of optical fibres on main routes. In an important contribution to achieving economical installation of these long systems, Telecom developed techniques for ploughing optical fibres directly into the ground, while ensuring that transient and residual strain on the fibres are limited to less than 0.2 per cent. The basic function of the catenary in the cable is to decouple the cable already in the ground and flowing through the cable box, from the high inertia of the cable drum. A light sensing arm SA which rides the cable is attached to a rotary potentiometer RP, while the angular position of sensing arm and rotary potentiometer indicates the reference position of the cable catenary. Any deflection of the sensing arm from its normal operating angle results in an error signal at the output of an error amplifier. After conditioning, this signal causes the electro-hydraulic drum drive to either pay out or wind in cable in order to return the sensing arm to its reference position. Response time between sensing arm movement and cable drum acceleration is 0.1 seconds.[58]As requirements for data services grew, the traditional methods of providing relatively slow speed transmission over the switched telephone network, and with individually leased lines for users requiring larger capacities, required upgrading. To achieve this, two new services, both relying essentially on imported technology, were introduced. AUSTPAC, a public switched data service on its own network, was introduced in 1982 to provide a universal, shared, intelligent network for switched data communications. It was based on a SESA (French) packet switching system DPS-25 and supplied through STC who contributed PCBs (printed circuit boards) and assembled and tested exchanges. As AUSTPAC was to be the basis for a range of new services such as Electronic Funds Transfer (EFT), including Point of Sale (POS), videotext services and electronic mail, interfaces to various other public networks, including the telephone and telex networks had to be developed as well as international interfaces to other countries' packet systems. In 1986 AUSTPAC had 20 exchange nodes in mainland capital cities with some 2000 direct connections, mainly X25 synchronous services, together with many applications using access through the PSTN.[59]
For larger users requiring dedicated data communication services, a Digital Data Network (DDN) was developed, based on a Teletra (Italian) design and supplied initially through AWA, who redesigned and manufactured the network terminating units, as well as manufacturing Zone Order Digital Multiplex Equipment. The system was designed to incorporate the following features:
- Rapid Service Provision,
- High standard of error performance (99.5 per cent error free seconds),
- High availability (99.9 per cent),
- Rapid service restoration.
Synchronous based service was offered initially at the data rates of 2400, 4800, 9600 bit/sec and 48 kbit/sec, with development to include:
- A Time Division Cross Connect system without demultiplexing.
- A management and control system to achieve large scale network surveillance.
- Customer distribution system for higher speed data rates of 48 kbit/s and above.
Organisations in Australian Science at Work - Amalagamated Wireless Australia (A.W.A.); Australian Post Office (A.P.O.); CCITT (International Consultative Committee for Telephony and Telegraphy); Overseas Telecommunications Commission (O.T.C.); Standard Telephones and Cables (S.T.C.); Telecom Australia (Australian Telecommunications Commission)
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Australian Academy of Technological Sciences and Engineering |  |
© 1988 Print Edition pages 593 - 595, Online Edition 2000
Published by Australian Science and Technology Heritage Centre, using the Web Academic Resource Publisher
http://www.austehc.unimelb.edu.au/tia/571.html