\draw (0,0) coordinate (a) to [short,o-*] ++ (0.75,0) coordinate (ai)
                           to [C,-,l=$C$] ++ (3,0) coordinate (bi)
                           to [short,*-o] ++ (0.75,0) coordinate (b);

\draw (ai) to [C,-,l=$C_{\mathrm{P,B}}$] ++ (0,-2)
           node[sground] {};
\draw (bi) to [C,-,l_=$C_{\mathrm{P,T}}$] ++ (0,-2)
           node[sground] {};

\node[anchor=east] at (a) {B};
\node[anchor=west] at (b) {T};