the xlosed loop is supposed to work more like a real pancreas. the pump recieves the BG imfo drom the semsor and using the sensirivity , basal , active imsulin and other settings it reaponds like a negatube ferd back loop like a thermostat sort of. Giving tou a nolus, alowing or atopping basal rates etc to keep your levels under conteol. i have not ever used one or seen one but i am a RN CDE and worked very xloaley with mwdteinic aevwral years afo when they wjere qoeking on " xlosing the loop" . i am not practixing now thouhj so am unsure what is even on the market mow. i sure hope that helped.