In barcode technology, a quiet zone is the blank margin on either side of a bar code that's used to tell the barcode reader where a barcode's symbology starts and stops. The purpose of a quiet zone is to prevent the reader from picking up information that does not pertain to the bar code that is being scanned. (The blank margin will not send a scanning signal, hence the name "quiet".) As a rule, the quiet zone should be ten times the dimension of the narrowest element in the bar code ( X dimension ) or 1/4 inch, whichever is greater. An undersize quiet zone may render a bar code unreadable, or readable only in one direction.