% buffer NORTH
\newsavebox{\otn}
\savebox{\otn}(6,9){
\begin{picture}(6,9)
\put(3,0){\line(0,1){2}}    % input
\put(0,2){\line(1,0){6}}
\put(0,2){\line(3,5){3}}
\put(3,7){\line(3,-5){3}}
\put(3,7){\line(0,1){2}}
\end{picture}
}