jQuery Droppable (Accept only one Draggable)

jQueryDroppable.js

$(".drop_area").droppable({
tolerance: "intersect",
accept: ".drop_item",
greedy: true,
	drop : function(event, ui) {
		$(this).droppable( "option", "disabled", true );
	},
	out : function(event, ui) {
		$(this).droppable( "option", "disabled", false );
	},
	revert: function (event, ui) { 
		$(this).droppable( "option", "disabled", true );
	}
});