Australia made use of the Over-the-Horizon radar program. In the early 1970s it constructed the Jindalee Operational Radar Network, which was somewhat experimental. It would watch for an attack by sea or air.
The range of these radars could be as far as 4,500 kilometres, reaching Singapore. The first station was in the middle of the landmass at Alice Springs and included a transmitter at Hart’s Range and a receiver 100 kilometres away at Mount Everard.