Before revision:  We explore the critical properties of random networks of such nodes and find a critical connectivity K_c=2.0 with activity vanishing at the critical point  .
After revision:  We explore the critical properties of random networks of such nodes and find a critical connectivity K_c=2.0 with activity vanishing at the critical point . Finally, we observe that the present model allows a more natural implementation of recent models of budding yeast and fission yeast cell-cycle control networks .