.PS
cct_init

# Usual defs...
qrt=dimen_/4;
hlf=dimen_/2;
dim=dimen_;

S1:source(up_ hlf, AC, qrt) 
llabel(,V_a)
line right_ dim/8 then up_ dim
line from S1.start right_ dim/8 then down_ dim

move to S1+(dim,0); right_
arrow "Energy" "Flow"

move to S1+(3*dim, hlf)
len=0.707*hlf;
S2:source(up_ len left_ len, I, qrt) 
rlabel(,I_b)
len=0.707*dim/8;
line left_ len down_ len
P1:Here
line from S2.start left_ len down_ len
len=0.707*dim
line down_ len right_ len
move to P1
line up_ len left_ len


move to S1+(5*dim,0)
{line dashed from Here - (0,1.5*dim) to Here + (0,1.5*dim)}
move right_ dim


S1:source(up_ hlf, I, qrt) 
llabel(,I_a)
line right_ dim/8 then up_ dim
line from S1.start right_ dim/8 then down_ dim

move to S1+(dim,0); right_
arrow <- "Energy" "Flow"

move to S1+(3*dim, hlf)
len=0.707*hlf;
S2:source(up_ len left_ len, AC, qrt) 
rlabel(,V_b)
len=0.707*dim/8;
line left_ len down_ len
P1:Here
line from S2.start left_ len down_ len
len=0.707*dim
line down_ len right_ len
move to P1
line up_ len left_ len

move to 5*dim, -2*dim ; right_
"$V_a$ causes $I_b$ ; $V_b$ causes $I_a$"; move down_ dim/3
"If $V_b$ is made = $V_a$, then $I_a$ will be = $I_b$"

"\tiny reciprocity" at (9*dim,-1.5*dim)
.PE