On 5/9/2007, Peter Tarver wrote:
If you had an opportunity to attend a 45 min. presentation on the safety of telecom as relates to 60950-x, what would you most want to have included? Hi Pete: I agree with Peter Merguerian that the classification of TNV-1, TNV-2, and TNV-3 circuits would be a good start, with a brief summary of isolation concepts such as creepage, clearance, hipot, and distance through solid insulation. With only 45 minutes total for the presentation, I would avoid getting mired down in the specific isolation requirements that typically apply to a given type of TNV circuit. There are just too many variables. Another key element would be to explain the circumstances under which isolation from SELV and ground is required and the circumstances where isolation is not required. As you know, many people assume that isolation is always required and that is not the case. Yet another key topic would be power cross compliance for UL 60950 and for Telcordia GR-1089. Most people conceptually understand the "no risk of fire" criterion but many do not understand the need for fusing for the M-1 test and the need to retain the integrity of the isolation barrier. If time permits, a brief reference to the "construction path" alternative in UL 60950 would be a good idea, since not all products incorporate fusing. When discussing fusing for power cross testing, it is worth mentioning that there may be conflicting non-safety criteria for lightning immunity that complicate the design process. I think it would be kind of fun to try and hit all the key points in 45 minutes. If that is your assigned task, I'd love to see what you come up with! Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected] http://www.randolph-telecom.com <http://www.randolph-telecom.com/> ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- 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/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] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
