\documentclass{ppex}
\nonstopmode
\usepackage [all,dvips]{xy}
\pagestyle{empty}

\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage [all,dvips]{xy}
\newcommand{\Neuron}[1]{\POS*+=<1em>[o]+[F]{#1}}
\newcommand{\Link}[1]{\ar @{-} "#1"}
\newcommand{\Out}{\ar +/r8mm/}
\newcommand{\In}{\save +/l9mm/*{}\ar +/r5mm/\restore}
\newgraphescape{O}[1]{!{\Neuron{#1}="#1"\Out}}
\newgraphescape{H}[1]{!{\Neuron{#1}="#1"\Link{A}\Link{B}}}
\newgraphescape{I}[1]{!{\Neuron{#1}\In\Link{a}\Link{b}\Link{c}}}
\[\xygraph{!{0;<18mm,0mm>:<0mm,10mm>::}
 [] !O{A}       [d]!O{B}
 [dd]*[left]!U[F]\txt<12mm>{output\\layer}="T"
"A" [u(.5)l]!H{a}
    [d]!H{b}    [d]!H{c}
"T" [l] *[left]!U[F]\txt<12mm>{hidden\\layer}
"a" [ul]!I{t_1}    [d] !I{t_2}    [d] !I{t_3}
    [d] !I{t_4}    [d] !I{t_5}
"T"[ll] *[left]!U[F]\txt<12mm>{input\\layer}
}\]
\end{document}