Each sensor contains a strip of electrodes. This one-piece unit is coated with a medical grade adhesive to establish electrical contact when placed on the forehead, and is designed for symmetrical placement to capture bi-hemispheric data. The sensor is attached via a cable to a VISTA stand alone unit module that serves as an interface between the sensor and the BIS monitor. This module is a signal converter, which acquires the electroencephalogram (EEG) signal from the sensors and converts the EEG signal to digital format. The EEG signal is then processed and the BIS index is played on the monitor. Data output (processed and raw EEG) will be downloaded.