Specialised infantry units of the Australian Army Reserve
The Regional Force Surveillance Units (RFSUs) are specialised infantry units of the Australian Army Reserve responsible for patrolling northern Australia. Collectively, the RFSUs form the Regional Force Surveillance Group commanded by a Colonel based at the 2nd Division Headquarters in Sydney. The RFSUs conduct regular operational patrols during peacetime, and are composed primarily of Reservists who live within the area of operations.
https://en.wikipedia.org/wiki/Regional_Force_Surveillance_Units