 Here, the neuron s (the switch) is special. It can either be set to the left or to the right, indicated by the direction the arrow is pointing. Likewise, the connection between f and s is special. If f fires, then s will be set to the right. If f does not fire, then s will be set to the left. On the other hand, the connection between p and s is normal. If p fires, then s will fire. If s fires while set to the left, then l will fire. If s fires while set to the right, then r will fire. If either l or r fires, then e will fire.