Signalling

The major visible developments in Australian railway signalling since then include colour-light signals; dc then ac then jointless high frequency track circuits; tuned reed and later multiplexed telemetry which made possible the remote control from a single panel of complete main lines (Centralised Traffic Control) and complexes of complicated interlockings in high traffic density territory (Area Signalling); track magnet operated automatic warning (the successor to train stops and tripcocks); and interlocking by miniaturised relays and switched contacts, instead of direct or power operated mechanical locks. All these developments were of overseas origin, and brought to Australia by the subsidiaries and licensees of the great signal engineering companies of the U.K., the U.S.A. and France.

Once again it was the application of these basic tools of technology that was Australian -and in some cases, the application was very innovative and novel. The use of computers in the control mode to store train descriptions and (if all is normal) to routinely select paths and direct the operation of points and signals, is one such instance. Lesser known is the development of computer-read system situation report-
ing, and computer-generated colour video displays of points, signalling, public information displays and a recent technique for voice synthesis station announcements. Solar power has likewise been applied to remote and isolated equipment locations.

Most of the real innovation in the decade to 1986, however, has been invisible. The pressure to economise in the use of interlocking relays (which are found by the thousand in complex area schemes and long CTC operated lines) has led to the abandonment of concepts of building one interlocking from multiple 'bricks' of standard functional assemblies, in favour of custom designing the circuits by computer, using CAD displays. Such innovations are novel and unlike the lineside signals and other hardware, are hidden in lineside 'location' huts, in downstairs relay rooms and even on the printed circuit boards in standard racks, that even to the experienced signal engineer, look much the same. Nonetheless, their use has made possible more extended application of modern signalling techniques in Australia than would have been economically possible as recently as 1975.

This trend is even more evident in the willingness to apply new technology, stimulated by economic pressures to avoid costly track circuits, relay complexes, and high volume data transmission lines in copper. Already all the Australian railways are using fixed microwave communications; several have fibre optic links in service and are seriously looking at radio operated single line safe-working; at least one uses Telecom STD links for electric staff operation and has reluctantly rejected train pinpointing location by satellite. Axle counting, and vehicle weighing by solid state transducer is the norm. Vehicle identification (automatic car identification) is likewise being applied.

The pressure for sound communications (in all forms, from teleprinter to data link) for effective operations has led the railways to replicate, in their own specialised systems, virtually every key communications technology found on the Telecom Australia networks -and to do this economically for (relatively) low volumes of intelligence. Increasingly, the electronic hardware is following the software in being Australian developed, as well as Australian made.

Australian Academy of Technological Sciences and Engineering