With the destruction of the Darwin Post and Telegraph Office by a direct hit during the first devastating Japanese air raid of 19 February 1942, Top End telegraph and telephone communications were cut during a critical period in the planning of Australia’s defence. Surviving Postmaster-General’s Department staff and equipment were relocated to the relative safety of Adelaide River Military Telephone Exchange where Rear Headquarters North Western Area was established during August 1942.
Among the telecommunications equipment transferred to military control were a state of the art telephone repeater system and a multi-channel voice communications system then in the course of completion. All PMG staff working at Adelaide River were evacuated to Adelaide in October 1942 amid false accusations of spying by the military. Telephone equipment in Adelaide River was initially housed in Sidney Williams huts. Between August and October 1943 a fortified concrete building was constructed into the hillside alongside the railway to serve as a telephone exchange for the North Western Area. Concrete blast walls shielding the doorways and wire supports for camouflage netting remain as evidence of the building’s strategic importance.