The SAS is made up of three main components that work together to monitor the subject's brain signals and then relay their information to the subject: the leads, the implantable telemetry unit (ITU), and the personal advisory device (PAD). The leads will be placed on different areas of the subject's brain to record electrical signals. The leads are tunneled down the neck to an ITU that is implanted in the chest, similar to a pacemaker. The ITU wirelessly transmits information to the PAD, which is carried like a pager. It records and processes brain signals and may be able to advise subjects when a seizure is likely or unlikely to occur.