The machine tells you whether a patient is brain dead or not.
No such machine exists. Dead people can't be used to donate most organs (I think perhaps corneas are one of a few exceptions). Your heart must be beating and you must be breathing for organs to be useful. If they wait for even 2 minutes after those functions stop, the organs receive too much damage for a transplant.
I have taken care of brain dead patients in preperation for transplant.
There is no muscle tone, there are no reflexes, If you touch the cornea they will not blink.
There is a significant difference between brain dead and brain injured.