% Author: Dr. Matthias Jung, DL9MJ
% Year: 2022
\begin{circuitikz}[step=\getDarcImageFactor cm]
    \tikzstyle{help lines}=[gray];
    \draw[style=help lines] (0,-3) grid (8,3);
    \draw (0,-3) rectangle (8,3);
    \draw[ultra thick, black] (0,0)
        sin ++(1,-2) cos ++(1,+2)
        sin ++(1,+2) cos ++(1,-2) 
        sin ++(1,-2) cos ++(1,+2)
        sin ++(1,+2) cos ++(1,-2);
    \draw[thick, Triangle-Triangle] (2,0) -- ++ (4,0);
    \draw[thick, Triangle-Triangle] (3,0) -- ++ (0,2);
    \node[draw,very thick,circle,black,fill=white,inner sep=2pt]() at (3, 1.0) {1};
    \node[draw,very thick,circle,black,fill=white,inner sep=2pt]() at (5, 0.0) {2};
    \draw (+7.75,-3.25) node[](){$t$};
    \draw (-0.25,+2.75) node[](){$U$};
\end{circuitikz}