How come a common 'Dhwaja sthambham'?

In temples we find one 'dhwaja sthambham' located for one 'Garbhaalayam', is it correct where there are more gods with more 'garbhalayams' and a common 'dhwaja sthambham' in a big compound area? What i heard was the gods 'drusti',which is powe oriented must straightly fall on 'dhwaja sthamba' located in front of the god. I wish enlightenment in this regard, what does the 'Aagama saastra says in this regard? And now a days temples are coming up in similar type of common compounds. Does 'silpa sastra' approves this?