Les built a detection, discrimination and analysis system based on Ashley and Paul's data and, much to his surprise at least, the first person (Lucy) connected to the system showed the capability of operating a switch which could control an electrical appliance. BACKGROUND - Technical Serious work done on brain signals began with Berger in 1929 [Berger 1967]. Since that time the acquisition and analysis of brain signals, referred to as Electroencephalography (EEG) has advanced to such a state that EEG is regularly used to assist in the diagnosis of schizophrenia, epilepsy and brain tumours. [Geddes and Baker, 1989]. EEG has also been used in biofeedback studies in which subjects may learn to modify their EEG signals in response to visual representation of their EEG signals. This control usually take weeks or months to learn and is not highly reliable. The system we have developed does NOT rely on any learned skill by an individual. It simply requires a person to close his/her eyes for more than 1 second to effect sufficient change in the signals levels to allow for the reliable operation of a switch. It turns out that it has been known for many years that increase in signal level occur upon eye closure, but this is the first example (to our knowledge) of the recognition of its potential and the exploitation of the effect. The system used to detect the change in signals consists of amplifiers, filters and other signal processing elements (full DETAILS ARE STILL CLASSIFIED at the moment!). As there are other sources which can generate signals which can interfere with brain signals (and hence cause intermittent switching on and off of appliances) we have developed a noise suppression system which eliminates the effect of those noise sources. This feature is very important as we are currently developing the technology for disabled persons (we have a three year grant from the Motor Accident Authority of New South Wales, MAA) and reliability is a major issue. The funding from MAA has allowed us to appoint Mr Andrew Searle who has become a key figure in the technical developments regarding the Mind Switch. -121-