A 'Phantom Scalp' was constructed from a conducting foam mat to form a layer under a 62-electrode electroencephalogram cap closely approximating the electrical properties of a human scalp. The mat was placed over a polystyrene manikin head to preserve a correct anatomical arrangement. Electrical signals were recorded with a Global System for Mobile (GSM) communications mobile phone handset in place against the side of the 'head'. Amplitude spectra were compared for three phone conditions: 'off', 'standby' and 'transmit'. At 217 Hz, significant differences were obtained between 'transmit' and the other two conditions, but no significant differences were noted for the physiologically important range 0.5–30 Hz. An anomalous difference was noted for one electrode in the range 30–45 Hz.