This image shows a Searchlight Control radar (unknown mark) attached to a standard 150 cm searchlight. The SLC system was nicknamed "Elsie".
<p>The transmitter antenna is at the very top, the other four antennas are receivers, two for the horizontal axis and two vertical. By comparing the returns from a pair of antennas, the operator could tell which direction to turn the radar to make the two signals equal, when this was accomplished both horizontally and vertically, the target would be close to the center of the searchlight beam, and could be tracked optically from that point.
</p><p>Later examples of the SLC system included a fifth antenna which received IFF signals. This was normally located beside the transmitter antenna, at the top.
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This example is shown on New Guinea, operated by the 73rd Anti Aircraft Searchlight Battery and used for airfield defence.
Donald Stewart Roberts
<a rel="nofollow" class="external free" href="https://www.awm.gov.au/collection/P05147.011">https://www.awm.gov.au/collection/P05147.011</a>