In an activity diagram, a signal receipt 
can be used to replace an event label on a transition.
Unlabeled transition arrows connect the Signal Receipt shape to the previous and next action states. You can also use a dependency to connect the notch to an object representing the sender of the signal.
Name a Signal Receipt shape and add other property values
Open the element's UML Properties dialog box by double-clicking the icon that represents the element in the tree view or the shape that represents the element in a diagram.
