 The indicator loop and photo-electric beam installation at Myrtletown was part of an interlocking system of naval defences for Moreton Bay, which incorporated coastal artillery batteries, indicator loops, controlled minefields, ASDIC (anti-submarine sonar detection) devices, Fairmile anti-submarine motor launches, a photoelectric (PE) beam and an anti-submarine boom.The place demonstrates rare, uncommon or endangered aspects of Queensland's cultural heritage.RAN Station 9 was one of only three PE beam harbour defence installations constructed in Australia during World War II.