node Tank
  state level : [0,nbSensors] : public;
  init  level := nbSensors/2;
  flow  input : [0,4];
        output : [0,2];
  event time;
  trans input>output |- time -> level := level + 1;
        input<output |- time -> level := level - 1;
        input=output & input=0 |- time -> ;
        input=output & input>0 |- time -> level := level - 1;
        input=output & input>0 |- time -> ;
        input=output & input>0 |- time -> level := level + 1;
	/* To avoid deadlocks */
	input>output & level=nbSensors |- time -> ;
	input<output & level=0 |- time -> ;
edon