There are three main systems of expressing the properties of a fourterminal network. In each the network is regarded as having an input voltage vi, an input current ii, an output voltage vo and output current io as illustrated in Fig. B.1.
In the first system the input and output voltages are expressed in terms of the input and output currents thus:
The factors zi, zr, etc., have the nature of impedances because, when multiplied by currents, ...