  \centerline{%
    \begin{tikzpicture}[scale=0.7,>=latex]
      \fill[gray!30] (0,0) -- (0,1.5) -- (1.2,1.5) -- (1.2,0);
      \fill[gray!60] (1.2,0) -- (1.2,-1.0) -- (3,-1) -- (3,0);
      %
      \draw (0,1.5) -- (1.2,1.5) -- (1.2, -0.8) -- (1.2,-1.0) --
      (3.0,-1.0) -- (3.0,0) -- (4,0);
      %
      \node (A) at (2.2,1.9) {\small $U_A T_1$};
      \draw[thin] (0.6,0.75) -- (A);
      \fill (0.6,0.75) circle[radius=0.7mm];
      %
      \node (B) at (3.5,0.8) {\small $U_B (T_2 - T_1)$};
      \draw[thin] (2.1,-0.5) -- (B);
      \fill (2.1,-0.5) circle[radius=0.7mm];
      %
      % horizontal axis
      \draw[->] (-0.2,0) -- (0.5+4,0) node[right] {$t$};
      \node at (1.2, -1.5) {$T_1$};
      \node at (3.0, -1.5) {$T_2$};
      \draw (4.0,0) -- (4.0,-0.1) node[below] {$T_s$};
      % vertical axis
      \draw[->] (0,-1.2) -- (0,2.0) node[above] {$u_L(t)$};
      \draw (0,1.5) -- (-0.1,1.5) node[left] {$U_A$};
      \draw (0,-1.0) -- (-0.1,-1.0) node[left] {$U_B$};
      \draw (0.6,-2.3) node[below] {$P_A T_s$};
      \draw (2.1,-2.3) node[below] {$P_B T_s$};
      %\draw (0,-1.8) to[out=-90,in=-90] (1.2,-1.8);
      \draw (0,-1.8) -- (0.2,-2.0) -- (1.0,-2.0) -- (1.2,-1.8);
      \draw (1.2,-1.8) -- (1.4,-2.0) -- (2.8,-2.0) -- (3.0,-1.8);
    \end{tikzpicture}
    \ind{15mm}
    \begin{tikzpicture}[scale=0.7,>=latex]
      \fill[gray!30] (0,0) -- (1.2,0) -- (1.2,1.5);
%      \node (A) at (0.2,-1.0) {\small från $U_A$};
%      \draw[thin] (0.8,0.5) -- (A);
%      \fill (0.8,0.5) circle[radius=0.7mm];
      %
      \fill[gray!60] (1.2,0) -- (1.2,1.5) -- (3,0);
%      \node (B) at (2.5,-1.0) {\small till $U_{ut}$};
%      \draw[thin] (1.8,0.5) -- (B);
%      \fill (1.8,0.5) circle[radius=0.7mm];
      %
      \draw[dashed] (0,0) -- (4, 5);
      \draw[dashed] (0,3.333) -- (4, 0);
      \draw[ultra thin,loosely dashdotted]  (4,0) -- (4,5.2);
      \draw[ultra thin,loosely dashdotted]  (0,5) -- (4.2,5);
      \draw (0,0) -- (1.2,1.5) -- (3.0,0) -- (4,0);
      % horizontal axis
      \draw[->] (-0.2,0) -- (0.5+4,0) node[right] {$t$};
      \draw (1.2,0) -- (1.2,-0.1) node[below] {$T_1$};
      \draw (3.0,0) -- (3.0,-0.1) node[below] {$T_2$};
      \draw (4.0,0) -- (4.0,-0.1) node[below] {$T_s$};
      % vertical axis
      \draw[->] (0,-0.2) -- (0,5.5) node[above] {$i_L(t)$};
      \draw (0,3.333) -- (-0.1,3.333) node[left] {$-I_B$};
      \draw (0,5) -- (-0.1,5) node[left] {$I_A$};
%      \draw (0,1.5) -- (-0.1,1.5) node[left] {$\max i_L$};
%      \draw (0.0,0) -- (-0.1,0) node[left] {$\min i_L$};
    \end{tikzpicture}
  }
