Common Detector Interface 2 (CDI2)

Project Owner: Federal Reserve System / European Central Bank 


CDI2 (Common Detector Interface 2) is a novel, open standard for high speed Banknote Sorting Machines (BSMs) that allows for:

  1. an easy integration of all types of detectors, including high quality camera systems for fitness detection, irrespective of the BSM or detector vendor.
  2. standardised access to the results and images of detectors for any central bank to implement their own algorithms or conduct data analysis.
  3. a flexible and powerful decision making logic allowing the central bank to adjust the BSM sorting logic according to their needs.

CDI2 has been developed jointly by the Federal Reserve and the Eurosystem. In 2017, after the publication of the first specifications, the two partners started a project to develop CDI2 Simulators to support vendors in implementing CDI2 into their detectors and BSMs. The project was completed successfully in November 2018 and the simulators are already being used by two major BSM manufacturers as well as a number of detector manufacturers to develop CDI2 compliant units. The developed set of Simulators includes also a mechanical note transport allowing for in-depth testing of new detectors prior to installation on a BSM.

Countr(ies) where implemented

So far the CDI2 Simulators have been produced in Austria by the Austrian Institute of Technology and in the Netherlands by De Nederlandsche Bank. These simulators are currently being used in the USA, Germany and France for the development of CDI2 compliant units.


In the past a BSM was typically a closed system with very limited access to data, adaptation of the sorting logic or the integration of new detectors (be it for fitness or authentication) requiring in-depth knowledge and support from the BSM vendor.
CDI2 marks a paradigm change, as it allows central banks and other commercial users of banknote sorting machines to be fully in control of their BSMs. CDI2 provides access to the underlying sorting logic, as well as the banknote image and sorting data. It gives central banks the possibility to install new compliant detectors on their own and offer new possibilities in data processing. Together with the now developed simulators including all underlying source code, vendors receive also technical support to implement CDI2 and deliver working solutions within the ongoing Federal Reserve’s tender for new sorting machines.

Differentiation of the innovation from existing processes, policies or products

Its predecessor, CDI1, was a specification that allowed adding in a simple way, authentication sensors to existing BSMs by defining a standardised communication interface and a mechanical outline. Now, CDI2 defines a complete architecture for the latest generation of BSMs covering also the integration of a high-quality camera system providing a full view of the banknotes. It also defines the communication between the BSM, all types of sensors and evaluation units.
It is the first time that central banks have teamed up to – as the customer – define standards according to their forward looking needs. Based on the feedback from the market, both central banks are very confident, that CDI2 will become the new, worldwide standard for (central bank) banknote authentication, putting central banks in the driver’s seat when it comes to processing banknotes in the most efficient manner.

Increased efficiency, effectiveness or environmental protection

The standardization introduced in CDI2 allows customers to select a BSM independent of the different detectors needed for fitness sorting or authentication. This opens the market for new detector manufacturers, especially those focussing on fitness detectors and industrial camera systems, providing additional innovative solutions at a level playing field to the existing vendors.
Also, it protects the capital investment into the BSM, as the transport function is disconnected from the detection. In case of technological developments CDI2 allows for a selective replacement of some detectors, keeping the underlying transport system in a simple manner, enabling an increased lifetime of sorting machines.
The open data architecture allows a central bank to use data analytics and improve their sorting processes by easily adjusting sorting thresholds, as well as the overall sorting logic down to the underlying fitness algorithms.

Important Improvement

The recent development of the CDI2 Simulators marks again the support of the FED and the ECB provided for CDI2. These Simulators have already been supplied to interested vendors to develop and test their CDI2 BSMs and devices.
Very importantly, the CDI2 specifications have been added as a mandatory requirement to the current tender of the Federal Reserve for a new banknote processing system.

Awards | Currency Awards 2019


Best Banknote Processing Innovation


Finalist | Winner