The operator of a certified aerodrome (a term that has replaced 'licenced aerodrome') that does not have a continuous air traffic service provided by ATC during the day must provide a signal area consisting of a black circle of 9 m diameter with either a 1 m white border or 6 white edge markers. The photo above shows the signal area at Narromine, NSW, in October 2007, an example of the latter style. The signal area replaced the earlier signal square.

The signals that must be displayed are a white cross if the aerodrome is unserviceable, a white dumb-bell if aircraft are only to use sealed movement areas, and a white double-cross when glider operations are being conducted. In the case of Narromine, a major gliding centre, the double cross symbol is permanently displayed. The other two symbols are, somewhat unusually, mounted on frames such that they can be rotated to display either a white or black face upward - both set to black in the photo above.

Behind the signal area is the aerodrome's primary illuminated wind indicator - read more here

(Photo: Phil Vabre)