In message <001d01c66781$124bafb0$13655ad2@LocalHost>, dated Mon, 24 Apr 2006, Kim Young-sik <[email protected]> writes >Hi, All > >When telecom line surge immunity test. > >unsymmetrically & symmetrically operated line??? > >what is that mean? > > 'Unsymmetrical' = 'unbalanced', the two conductors have different impedances to whatever is regarded as 'earth' or 'ground' in the system.
'Symmetrical' = 'balanced', the two conductors have very nearly equal impedances to whatever is regarded as 'earth' or 'ground' in the system. Not that the terms don't say anything about the voltages or currents on the conductors; balance is entirely about impedances. This is not widely understood. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - 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
