The defined scattering parameters are also vector quantities. Nominally, it is assumed that port one is the input port, and port two is the output port. Using this assumption, S11 is the input reflection coefficient, and S22 is the output reflection coefficient of the two port network. The transducer power gain is defined as the power delivered to the load divided by the power available from the source. Using network analysis flow graphs, the expression for the transducer gain is: