.PS
  command "/Times-Italic findfont 11 scalefont setfont"
  arrow "u" above
S: circle rad 10/72.27  # 10 pt
  line right 0.35
G: box "G(s)"
  arrow "y" above
  line down G.ht from last arrow then left last arrow.c.x-S.x then to S.s
  move down 0.05 left 0.15; ""
  command "(\261) show"
  arrow <- down 0.1 from S.s
.PE
