.PS
{box
arrow right from 1/3 of the way between last box.ne and last box.se
arrow right from 2/3 <last box.ne,last box.se> }

move right 2
A: ellipse
   ellipse ht .2 wid .3 with .se at 1st ellipse.nw
   ellipse ht .2 wid .3 with .sw at 1st ellipse.ne
   circle rad .05 at 0.5 <A.nw,A.c>
   circle rad .05 at 0.5 <A.ne,A.c>
   arc right rad .3 from 0.25 <A.w,A.e> to 0.75 <A.w,A.e>
.PE
