Du kannst die nodes benennen und entsprechende Annotationen vornehmen.
[![alt text][1]][1]
%\documentclass{article}
\documentclass[circuitikz, margin=5mm]{standalone}
\documentclass[margin=5mm]{standalone}
\usepackage{siunitx}
\usepackage{circuitikz}
%\usepackage[symbols]{circuitikz}
\usepackage{tikz}
\usepackage{lmodern} % <------ "\sffamily\slshape\bfseries"
\begin{document}
\ctikzset{bipoles/thickness=1} % <------ normale line width
\begin{circuitikz}[>=latex,
font=\sffamily\slshape\bfseries,
thin,
common/.style={fill=white, font=\sffamily\slshape},
pStyle/.style={text=blue, common},
qStyle/.style={text=red, common},
]
\draw
(0,0) node[] (UL) {} % <------
to[short, o-*] (3,0)
to[C, l={C}, *-*] (3,2)
(3,0) to[short, *-o] (4,0) node[] (UR){} % <------
(0,2) node[] (OL) {} % <------
to[short,o-](0.4,2)
to[R, l_={R}, -](1.5,2) % <---
to[L, l_={L},-*](3,2) % <--
(3,2) to[short, *-o] (4,2) node[] (OR){}; % <------
\tikzset{every path/.style={very thin}}
\draw[<->] (UL) -- (OL) node[midway, pStyle]{p$_\textsf{in}$};
\draw[<->] (UR) -- (OR) node[midway, qStyle]{p$_\textsf{out}$};
\draw[->, transform canvas={yshift=5mm}] (OL.center) -- +(7mm, 0) node[ anchor=west, qStyle]{q$_\textsf{in}$};
\draw[<-, transform canvas={yshift=5mm}] (OR.center) -- +(-7mm, 0) node[ anchor=east, pStyle]{p$_\textsf{out}$};
\end{circuitikz}
\end{document}
[1]: https://texwelt.de/upfiles/56555555.png
