On 11/14/2006, Naftali Shani wrote:
Probing the collective knowledge of the group here: which are the known countries/regions/carriers/etc that still run their COs from nominal -60 VDC? If memory serves me correctly (as of the last millennium) there were some locations in Germany and Austria – is this still true? Hi Naftali: In the 1997 edition of ETS 300 001 (Net 4) that I have on file, the 60 VDC feed is listed for Austria, Bulgaria, Czech Republic, Germany, Greece, Luxembourg, and possibly Norway. I believe that 60 VDC continues to be used in Germany, Austria, and the Czech Republic, but it may be in the process of being phased out in the other countries listed. Perhaps you can clarify what aspects of the "SELV vs. TNV-2 debate" apply to your application. If you are connecting to outside lines from a C.O., the question should really be "TNV-1 vs. TNV-2," since outside lines can not usually be classified as SELV. Under the definition of TNV-2 in EN 60950, up to 120 VDC is allowed (as opposed to 60 VDC in UL 60950). If your application is within the C.O., there are two classification approaches that I have seen used: 1) Classify the input as SELV rated at 60 VDC, and treat the higher voltages (up to 72 volts under float) as abnormal levels and test them that way. 2) Classify the input as TNV-2 and design accordingly. In general, I favor Option #2. If the equipment will be used inside a C.O., you have many degrees of freedom in terms of grounding and the exclusions available due to the limited access nature of the installation. It may turn out that the design does not need to be changed very much in order to support a TNV-2 classification. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) j...@randolph-telecom.com 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
