Most current rosters are 4 on 2 off (but it varies 5 on 2 off 3 on 1 off etc)...
There is currently an expectation that you be available except in specific circumstances for overtime on your days off (as recently confirmed by the AIRC). That doesn't mean you always get called when you're off...
The maximum run of consecutive shifts is 10; so you get one off after ten on guaranteed!