u := 2.5cm;
r := 0.5cm;

beginfig(1);
z0=(0,0);
z1=(u,0);
draw  for theta=0 step 10 until 350:  z0+r*dir theta..  endfor  cycle;
draw  for theta=0 step 10 until 350:  z1+r*dir theta..  endfor  cycle;
draw  for theta=0 step 10 until 350:  z1+0.8r*dir theta..  endfor  cycle;
drawarrow z0+0.5u*dir180--z0+r*dir180;
path p;
p:=z0+r*dir30{dir30}..{dir-30}z1+r*dir150;
drawarrow p;
label.top(btex$\tt0$etex, point 0.5 of p);
p:=z1+r*dir-150{dir-150}..{dir150}z0+r*dir-30;
drawarrow p;
label.bot(btex$\tt0$etex, point 0.5 of p);
p:=z0+r*dir142.5{dir142.5}..{dir-112.5}z0+r*dir67.5;
drawarrow p;
label.top(btex$\tt1$etex, point 0.5 of p);
p:=z1+r*dir37.5{dir37.5}..{dir142.5}z1+r*dir-37.5;
drawarrow p;
label.rt(btex$\tt1$etex, point 0.5 of p);
label(btex$A$etex, z0);
label(btex$B$etex, z1);
endfig;

bye