Double-feed detection

The Duo Reader is used in mail sort operations to detect double-feeds when the de-stacker pulls more than one item from the input hopper into the mail transport. The system is supplied with an industry-standard PC and Windows software and the reader head is focused for life before it leaves the factory. Different shape reader heads are available for integration onto a range of sorting machines.

The Duo Reader speeds up processing and the very low false double and missed double error rates give improved quality of service and fewer sorter jams. The Duo Reader is compact and easy to retrofit, and its integrated design means no customer calibration is necessary. The patented side-view optics allows the Duo Reader to perform well on tabbed and folded mail items.

The image above shows 6 items de stacked at once – without a Duo Reader this group of 6 letters would result in 5 mis-sorted letters, or jam the sorter. Both jams and mis–sorts are reduced by the Duo Reader.

  • Selected by United States Postal Service (USPS) after competitive trials against Omron and Siemens devices, over 1700 units supplied to USPS.
  • Wessex estimates 200,000,000 doubles decisions made every 24 hours in the USPS.
  • Very reliable and with a high degree of software stability, USPS has requested no software changes in the last 6 years.
  • In the USPS the Duo SV is working on street collection mail and bulk mail – the world’s most challenging mail base.
  • Patented side view optics means that tabs can be easily detected on bi-fold mail, giving a low rate of false detects.
  • Selected as the “design in” detector by two sorter builders
  • Calibrated for life in manufacture – no in service adjustments giving consistent performance and negligible service costs.
  • Duo SV was originally designed to be an after market retrofit – hence it’s small size.
  • The PC used is fanless and has solid state drive for maximum reliability.
  • A range of interfaces is available, RS232, Ethernet, RS422.


For information about the United States Postal Service Duo project click here

To find out more about the Duo-Reader from Wessex Technology, email or contact us.

For information about the software releases since release to United States Postal Service click here