This equivalent circuit for Z-parameters of a two-port network. The drawing was done in Latex using the following code:
\documentclass{article}
\usepackage{tikz}
%%%<
\usepackage{verbatim}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{10pt}%
%%%>
\usepackage[europeanresistors,americaninductors]{circuitikz}
\begin{document}
\title{Thevenin equivalent circuit for Z-parameters of a two-port network using controlled sources}
\author{Dalba}
\begin{circuitikz}[american voltages]
\draw
(0,0) to [open, v^>=$V_1$] (0,3)
(0,0) to [short, o-] (3,0)
to [cV, l=$Z_{12}I_{2}$] (3,3)
to [R, -o, l_=$Z_{11}$, i_<=$I_1$] (0,3);
\draw[dashed]
(3,0) -- (6,0);
\draw
(6,0) to [cV, l_=$Z_{21}I_{1}$] (6,3)
to [R, -o, l=$Z_{22}$, i^<=$I_2$] (9,3)
(6,0) to [short, -o] (9,0)
(9,0) to [open, v_>=$V_2$] (9,3);
\end{circuitikz}
\end{document}