We are all familiar with the Cerebro device used by the Professor in X-Men comics/movies. A similar but more realistic equipment is the brain computer interface or BCI. It has many other names like the human-computer interface or man-machine interface and so on. Technically, the BCI is a signal processing system that enables information exchange between the human brain and a central processing unit. In other words, this device permits humans to 'talk' to machines without any natural speech or actions. It uses the electric signals generated from the human brain to recognize the subject's intends. The signal collection is usually performed through electroencephalography or EEG. All BCIs that exist today are unidirectional, i.e, they can allow the machine only to hear the human brain 'talk', but cannot 'talk back'.
