An extensive form representation of a signalling game
Starting at the centre, Nature (N), moves first, choosing left and right with probabilities p and (1-p). 
Player 1 (1) moves next with either A or B. 
Player 2 (2) does not know which option was selected by Nature (indicated by dotted lines) and chooses either X or Y. 

The payoffs for Players 1 and 2 are denoted at the end of each branch.
Own work
Kevin Zollman --Kzollman