Hello Doug, I have only a limited amount of knowledge in this area, and I hope another listserv member can either correct me or provide more detail. I also believe Mike Sherman may be correct on the knife edge/finger stock description.
The CDRH at the FDA is generally very conservative and they don't update requirements often as technology changes. (Their inspection guide<https://www.fda.gov/downloads/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/UCM135868.pdf> still dates from 1985.) I believe that the restrictions on interlock type is based on making it difficult to override the interlock. I do believe that your interpretation is correct. The interlocks you show should meet the CDRH requirements. Ted Eckert Microsoft Corporation The opinions expressed are my own and do not necessarily reflect those of my employer or the FDA. From: Doug Nix <[email protected]> Sent: Tuesday, February 5, 2019 8:36 AM To: [email protected] Subject: [PSES] A question about FDA language and interlocking devices Colleagues, I had a question come my way yesterday that I need a little help with. Here's the question: I have a customer that produces X-ray equipment. The FDA requires that the door that gives access to the X-ray source must have an interlock with a 'knife-edge and finger stock' type connection. Also the FDA mentions that interlocks should be of conventional design. What is understood by "conventional design"? My reading on this requirement is that any conventional electromechanical interlocking device like this: [Image result for keyed interlock switch images] will meet the basic requirements as described by the FDA as "knife-edge and finger stock" connection, but I am concerned that this may not be at all what is meant. As always, any guidance you can offer will be welcomed and appreciated! Best, Doug Nix [email protected]<mailto:[email protected]> +1 (519) 729-5704 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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