PS
# Three.m4: three-phase oscillator
 cct_init

definergbcolor(Dandelion,0.825,0.825,0)
define(`section',`[ I: Here
 resistor(right elen_*0.75); llabel(,R/2)
T: dot
 line down dimen_/2 then right_ dimen_/4
 Amp: opamp(,,,body=shaded "Dandelion") with .In1 at Here
 line left dimen_/4 from Amp.In2 then down dimen_/4; G: ground
 resistor(from T to (Amp.Out,T)); llabel(,R)
O: dot
 { arrow up dimen_*0.5 then right dimen_/4 up dimen_/4
   "$`$1^\circ'$" above }
 line to Amp.Out
 dot(at T+(dimen_/4,0)); line up dimen_*0.6
 capacitor(right_ Amp.Out.x-Here.x-dimen_/4,C); llabel(,2C)
 line to (Here,T); dot
 ]')

A: section(0)
B: section(120) with .I at A.O
C: section(-120) with .I at B.O

 ground(at (A.I,A.G)+(dimen_/3,0),,)
P:potentiometer(down_ dimen_/2,,0.75,dimen_/2) with .End at Here
 line from P.Start to (A.I,P.Start); dot
 resistor(up_ dimen_*0.75 from P.T1)
 line to A.T

 dot(at B.Amp.Out+(dimen_/3,0)); { "$V_c$" above }
 resistor(down_ dimen_*0.75)
 { dot; line right (C.T.x-Here.x)/2
   reversed(`diode',up_ dimen_)
   line to C.T }
 resistor(down_ dimen_*0.75)
 dot
 line from C.O right dimen_/4 then down C.O.y-Here.y then to (A.I,Here) \
   then to A.I
PE