anchor.diff:  
   (defmethod lock-port ((p person) (voice-out voice-out-port)
   		      (vo voice))
  -  (setf (lock-of voice-out) t)
     (list (make-instance 'event
   		       :owner p
   		       :time (+ (clock-of p)
  
positive.code: 		 :a-can (make-instance 'can)
  		 :b-can (make-instance 'can)
  		 :wire (make-instance 'wire)))
  
negative.code:     :type voice-in-port)
     (voice-out
      :accessor voice-out-of
      :type voice-out-port)
     (reply-timeout
      :accessor reply-timeout-of
      :type event)))
  
  
  (defclass can (simulator)
  