A magnetic guide on a cane for blind people is being patented by the
Minnesota Mining and Manufacturing company of St Paul (WO 97/33548). The tip of
the cane contains a sensor that measures the strength of a magnetic field along
a guide track.
The track is made from three parallel strips, two outer regions which are
strongly magnetised and a central region which is lightly magnetised. The cane
emits a tone that changes with the strength of the field, keeping the user on
track.
