Hello All, I don't know what fire enclosure means in practice. Could someone familiar with the subject tell me if I should expect that Pen-drive I use has the fire enclosure or not ? Does it depends on material only, or is it impossible with so small dimensions. Regards, Piotr Galka
----- Original Message ----- From: [email protected] To: [email protected] ; [email protected] ; [email protected] Sent: Friday, December 17, 2004 9:59 PM Subject: Re: USB interface Limited Power source ? Kris, >From your reply below it sounds as though the answer to your question may not be found by considering only the requirements of standards, but also the requirements of legislation: for Europe the General Product Safety Directive and the Product Liability Directive. Let us say that you are responsible for designing a USB 'current sink' device and you have concluded that all USB current sources are LPS per IEC/EN 60950-1 and therefore you decide not to provide a fire enclosure. Now let us say that you sell your product in the EU (or the USA) where there are laws of 'strict liability' where it not necessary to prove that any injury resulted from product failing to comply with a particular standard, only that that an injury was caused and that, beyond reasonable doubt, the cause of the injury was your product. So, one day, one of your customers connects your product to a USB source and leaves it powered overnight and during that time there is a fault which causes a fire. Your defence is "not my fault, the source wasn't current limited as I expected". If you think that the probability of the above scenario is very small and so the cost of providing a fire enclosure is greater than any potential legal fees and loss of good name then you have one solution, if not you have another. Compliance with standards is just one tool, there are other considerations that should be taken into account. Regards, Richard Hughes In a message dated 12/17/2004 17:25:58 GMT Standard Time, [email protected] writes: Hi Dough, Thanks for you clear explanation. The problem I have is not really with the USB host device, but with the devices connected to it. If I can assume that the power on a USB interface can be considered as LPS, then the slave device - that can be connected to any PC host - doesn't need a fire enclosure. Some safety labs accept a USB to be LPS, some don't. You say - correct me if my interpretation is wrong - that the power on the USB bus is LPS unless some designer made a mistake in a host equipment by not adding protection elements. But than, this device does not comply with the USB spec and isn't a USB host device at all. Regards, Kris ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
