For products of different types and from different manufacturers to be able to perform various tasks in the automation process correctly, they must exchange information over the bus without errors. A prerequisite for this is a standards-compliant implementation of the communication protocols and application profiles by the device manufacturers. Vendor's products are submitted to and tested by an independent, accredited PI Test Lab, and successfully-tested devices are issued with a Certificate by the PI certification body to prove conformity with the communication and profile specifications. This provides the user with added peace of mind with respect to the interoperability and interchangeability of products. The certification procedure is based on standard EN 45000. In accordance with the requirements of this standard, the test laboratories accredited by PI are not aligned with any specific manufacturer. Only accredited test laboratories are authorized to carry out the device tests that form the basis for certification.