\documentclass{article}
\usepackage{tikz}
%%%<
\usepackage{verbatim}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{10pt}%
%%%>
\usepackage[europeanresistors,americaninductors]{circuitikz}
\begin{document}

\title{Equivalent circuit for Z-parameters of a reciprocal two-port network}
\author{Dalba}

\begin{circuitikz}[american voltages]
\draw
  (0,0) to [short, o-o] (8,0)
  (4,0) to [R, *-*, l_=$Z_{12}$] (4,3)
  (4,3) to [R, -o, l_=$Z_{11}-Z_{12}$] (0,3)
  (4,3) to [R, -o, l^=$Z_{22}-Z_{12}$] (8,3)
  ;
\end{circuitikz}

\end{document}