So you're out flying and your radio quits. Some how the tower notices this and shines a steady red light at you. So you circle. Do you fly a holding pattern, fly 360s, fly the traffic pattern but do not descend, obit the field three miles out? Circling is a very broad term. At some point the tower gets tired of you and realizes you're not going to depart the area for the uncontrolled field 10 miles away so they flash the green light at you. So now you set up for landing and you hope to see a steady green light on final.