I agree with Paolo, the definition refers to a shielded TWISTED-PAIR cable. Note also that twisted pair is hyphenated. While the definition might better have been worded to refer to 'one or more TWISTED-PAIRS, each of which...' rather than 'elements' it is not difficult to argue that the intention was that an 'element' was refering to a 'twisted-pair' and not each wire of the twisted pair/s. One might also argue that a cable is not a cable unless made of more than one separately insulated wires, but this is a somewhat more tenous argument. Dave
Paolo Roncone wrote: > > Doug, > > I re-paste the first part of the definition in IEEE 802.3 (2000): > > <<1.4.249 shielded twisted-pair (STP)cable: An electrically conducting > cable,comprising one or more ele- > ments,each of which is individually shielded.There may be an overall > shield,in which case the cable is > referred to as shielded twisted-pair cable with an overall shield > (from ISO/IEC 11801:1995)>> > > My understanding is that "elements" should refer to individual PAIRS > (signal/return), rather than single wires. But - as I said in my > previous e-mail - I'd like to check whether this is put into practice > by some vendors. So far I didn't get any clue on this. > The STP cables that I found so far (form a couple of vendors) have > just an OVERALL shield around all wires, and these are identical to > FTP (Foiled Twisted Pair) cables that are also on the market. > I agree with you, something doesn't sound right... > > Paolo > > At 09:36 05/09/2001 -0700, Doug McKean wrote: > > Paolo Roncone wrote: > > > > The reason of my inquiry is that we bought samples of > "STP" and > "FTP" > > cat.5 cables for 10bT ethernet applications from different > vendors > and to > > our surprise we discovered that both "STP" and "FTP" types > have an > > overall (external) shield made of aluminum foil, but no > shields on > individual > > wires or wire couples (as per 802.3 definition above). > > Maintaining a characteristic impedence of a twisted pair > by shielding the individual wires of that twisted pair? > > Something doesn't sound right. > > - Doug McKean > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: > http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: pstc_ad...@garretson.org > Dave Heald davehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web > at: > No longer online until our new server is brought online and > the old messages are imported into the new server. > > ------------------------------------------------------------------------------- > Paolo Roncone > EMC Compliance Engineer - Cisco Photonics Italy > via Philips 12 - Monza (MI) 20052 > mailto:pronc...@cisco.com > phone: +39 039209 1538 > fax: +39 039209 2036 -- Regards Dave Instone. Compliance Engineer Storage Systems Development, MP24/22 Xyratex, Langstone Rd., Havant, Hampshire, P09 1SA, UK. Tel: +44 (0)23-92-496862 (direct line) Fax: +44 (0)23-92-496014 http://www.xyratex.com Tel: +44 (0)23-92-496000 ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
