A portable electrically-powered device designed for recording of electroencephalographic signals in ambulatory patients for periods usually from 24 to 72 hours to assess a variety of neurological conditions (e.g., epilepsy) and psychiatric disorders; it is not intended for inpatient monitoring. It is a small unit designed to be worn by the patient with an appropriate signal amplifier, and intended to be used with a set of scalp electrodes that are placed on the cranium of the patient. The resulting electroencephalogram (EEG) data is analysed after the recording period using an appropriate computer/software.