This is an audio frequency magnetic recording made on a stop-start train journey from Farnborough To Woking UK. It was done on a fairly modern Network Southeast third rail pickup train. You can hear various elements of the magnetic environment including, turning off my mobile, walking through the train at the start, basic mains hum, variable frequency motor drive under park and acceleration, the constant scratching of the third rail pickup shoe, electrical braking, the eerie wail of passing signal gantrys and trackside equipment etc. The magnetic pickup is shown in the picture and is four radio ferrite rods arranged tetrahedrally with mains transformer primaries mounted on the centre of them inside the sphere. Each coil simply connects to WXY and Z on the recorder. The aluminium foil provides an electrostatic screen. (Any discussions regarding the technical accuracy of this arrangement may be addressed to British Airways Customer Care, 3 Ingrams Drive, Essex.) Now, where did I put my anorak?