SIGNAL-FLOW GRAPHS AND APPLICATIONS A signal-¯ow graph is a graphical means of portraying the relationship among the variables of a set of linear algebraic equations. S. J. Mason originally introduced it to represent the cause-and-effect of linear systems. Associated terms are de®ned in this chapter along with the procedure to draw the signal-¯ow graph for a given set of algebraic equations. Further, signal-¯ow graphs of microwave networks are obtained in terms of their S-parameters and associat