UK security printer De La Rue of Basingstoke, Hampshire, has invented a banknote that helps blind people recognise which notes they are handling (GB 2400074).
Its idea is to emboss a pattern of troughs and ridged lines, like miniature furrows in a field, at both ends of a banknote. When the note is folded in half, rubbing the two ridged areas together between finger and thumb will create a characteristic chirping sound. Notes of different value would have different ridge patterns and so make different sounds.
