RE: STP vs FTP Ethernet cables (2)
In fact a standard for 150 Ohms STP cable does exist but is intended for FDDI Token Ring applications, to which the ANSI X3.263 standard applies, and I assume not for Ethernet. Maybe the story I heard was about someone who used this type of cable for Ethernet. Although it was a logical guess, the 150 ohms value is not from the combination of the 100 ohm characteristic impedance and the 50 ohm output from equipment. Sorry for the confusion, Eric -Original Message- From: KC CHAN [PDD] [SMTP:kcc...@hkpc.org] Sent: Sunday, September 09, 2001 8:52 PM To: pronc...@cisco.com; james_al...@milgo.com Cc: emc-p...@majordomo.ieee.org Subject:RE: STP vs FTP Ethernet cables (2) I guess this 150 ohms is from the combination of the 100 ohm characteristic impedance and the 50 ohm output form equipment, like the power amplifier for conducted immunity test. Allan, James james_al...@milgo.com 09/07/01 09:03pm Paolo: Try this link to Quabbin wire company. It is a product selector guide with the types of wire used for different applications. All Ethernet applications are 100 ohm characteristic impedance and only have overall shields if shielded. Telecom cable (T1, DSL etc.) if shielded, are also 100 ohm but the shield (if present) is over the individual wire pairs with no overall shield. I find no reference to standard Ethernet cable at 150 ohms. LINK http://www.quabbin.com/finder/finder.cgi?cmd=app_form Jim Allan Manager, Engineering Services Nextira Solutions LLC 1619 N Harrison Parkway Sunrise, FL, 33323 E-mail james_al...@milgo.com Phone (954) 846-3720 Fax (954) 846-6282 -Original Message- From: Paolo Roncone [SMTP:pronc...@cisco.com] Sent: Friday, September 07, 2001 5:28 AM To: Meunier, Eric Cc: emc-p...@majordomo.ieee.org Subject: RE: STP vs FTP Ethernet cables (2) Eric, this 150 ohm story of STP cables sounds completely new to me. Also, my understanding is that both UTP and STP are used for 10bT ethernet. In the STP definition of IEEE802.3, there is no mention about different characteristic impedances from the required 100ohm of 10bT. Unfortunately I haven't yet received an answer to my original question as to how STP cables should be actually made (shielded twisted pairs vs overall shield) . As I already said in previous e-mails, the STP cables that I got look pretty much the same as FTP cables, that is they have just an overall shield (aluminum foil) around all wires. And they are all declared to be 100 ohms. Paolo At 16:56 06/09/2001 -0400, you wrote: Paolo, You may want to check if the FTP cable has a 100 Ohms characteristic impedance which would make it compatible with interfaces designed for UTP cable. STP cable is supposed to have a 150 Ohms impedance which is not compatible with standard 10baseT interfaces which are usually designed for UTP. Eric === Eric Meunier Hardware Architect E-mail: eric.meun...@ca.kontron.com mailto:emeun...@teknor.com Kontron Communication Inc. (Teknor) 616, rue Cure-Boivin Boisbriand, Quebec Canada, J7G 2A7 Tel: 1-450-437-4661 ext. 2419 Fax: 1-450-437-8053 Web: http://www.teknor.com/ http://www.teknor.com/ -Original Message- From: Paolo Roncone [SMTP:pronc...@cisco.com] Sent: Thursday, September 06, 2001 4:18 AM To: Doug McKean Cc: EMC-PSTC Discussion Group Subject:Re: STP vs FTP Ethernet cables (2) 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
RE: STP vs FTP Ethernet cables (2)
I guess this 150 ohms is from the combination of the 100 ohm characteristic impedance and the 50 ohm output form equipment, like the power amplifier for conducted immunity test. Allan, James james_al...@milgo.com 09/07/01 09:03pm Paolo: Try this link to Quabbin wire company. It is a product selector guide with the types of wire used for different applications. All Ethernet applications are 100 ohm characteristic impedance and only have overall shields if shielded. Telecom cable (T1, DSL etc.) if shielded, are also 100 ohm but the shield (if present) is over the individual wire pairs with no overall shield. I find no reference to standard Ethernet cable at 150 ohms. LINK http://www.quabbin.com/finder/finder.cgi?cmd=app_form Jim Allan Manager, Engineering Services Nextira Solutions LLC 1619 N Harrison Parkway Sunrise, FL, 33323 E-mail james_al...@milgo.com Phone (954) 846-3720 Fax (954) 846-6282 -Original Message- From: Paolo Roncone [SMTP:pronc...@cisco.com] Sent: Friday, September 07, 2001 5:28 AM To: Meunier, Eric Cc: emc-p...@majordomo.ieee.org Subject: RE: STP vs FTP Ethernet cables (2) Eric, this 150 ohm story of STP cables sounds completely new to me. Also, my understanding is that both UTP and STP are used for 10bT ethernet. In the STP definition of IEEE802.3, there is no mention about different characteristic impedances from the required 100ohm of 10bT. Unfortunately I haven't yet received an answer to my original question as to how STP cables should be actually made (shielded twisted pairs vs overall shield) . As I already said in previous e-mails, the STP cables that I got look pretty much the same as FTP cables, that is they have just an overall shield (aluminum foil) around all wires. And they are all declared to be 100 ohms. Paolo At 16:56 06/09/2001 -0400, you wrote: Paolo, You may want to check if the FTP cable has a 100 Ohms characteristic impedance which would make it compatible with interfaces designed for UTP cable. STP cable is supposed to have a 150 Ohms impedance which is not compatible with standard 10baseT interfaces which are usually designed for UTP. Eric === Eric Meunier Hardware Architect E-mail: eric.meun...@ca.kontron.com mailto:emeun...@teknor.com Kontron Communication Inc. (Teknor) 616, rue Cure-Boivin Boisbriand, Quebec Canada, J7G 2A7 Tel: 1-450-437-4661 ext. 2419 Fax: 1-450-437-8053 Web: http://www.teknor.com/ http://www.teknor.com/ -Original Message- From: Paolo Roncone [SMTP:pronc...@cisco.com] Sent: Thursday, September 06, 2001 4:18 AM To: Doug McKean Cc: EMC-PSTC Discussion Group Subject:Re: STP vs FTP Ethernet cables (2) 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
RE: STP vs FTP Ethernet cables (2)
ANSI X3.263 section 9.1.1.1 specifies that STP interfaces shall be terminated in 150 Ohms and section 9.1.2.1 that UTP shall be in 100 Ohms for qualification testing. It seems that most Shielded Twisted Pair cables on the marked called by the STP acronym are in fact designed according to UTP requirements such that they can be used for standard 10bT applications. I remember seeing a reference about this in a cable catalog, probably Belden, and I was told once that some people got trouble because they had used 150 Ohms STP cable on a 10bT LAN... which all seems to corroborate with the ANSI spec. If someone has time to investigate further... About the wavelengths comment, I guess it is true that one might typically get away with a few wavelengths for a 1.5 impedance mismatch ratio. However, if you want to be sure you will never get a surprise with equipment interoperability I would guess it is better to avoid such significant mismatch over more than a fraction of a wavelength. Equipment manufacturers design for 100 +/-15 Ohms cable impedance. Has anyone got field experience for large volumes and multiple interface vendors about this? Finally, if you are only concerned about getting a waiver for the Intra-building surge requirement, an overall shield would probably do and should be cheaper. Best regards, Eric === Éric Meunier Hardware Architect E-mail: eric.meun...@ca.kontron.com mailto:emeun...@teknor.com Kontron Communication Inc. (Teknor) 616, rue Curé-Boivin Boisbriand, Québec Canada, J7G 2A7 Tel: 1-450-437-4661 ext. 2419 Fax: 1-450-437-8053 Web: http://www.teknor.com http://www.teknor.com -Original Message- From: Allan, James [SMTP:james_al...@milgo.com] Sent: Friday, September 07, 2001 9:04 AM To: 'Paolo Roncone' Cc: emc-p...@majordomo.ieee.org Subject:RE: STP vs FTP Ethernet cables (2) Paolo: Try this link to Quabbin wire company. It is a product selector guide with the types of wire used for different applications. All Ethernet applications are 100 ohm characteristic impedance and only have overall shields if shielded. Telecom cable (T1, DSL etc.) if shielded, are also 100 ohm but the shield (if present) is over the individual wire pairs with no overall shield. I find no reference to standard Ethernet cable at 150 ohms. LINK http://www.quabbin.com/finder/finder.cgi?cmd=app_form Jim Allan Manager, Engineering Services Nextira Solutions LLC 1619 N Harrison Parkway Sunrise, FL, 33323 E-mail james_al...@milgo.com Phone (954) 846-3720 Fax (954) 846-6282 -Original Message- From: Paolo Roncone [SMTP:pronc...@cisco.com] Sent: Friday, September 07, 2001 5:28 AM To: Meunier, Éric Cc: emc-p...@majordomo.ieee.org Subject: RE: STP vs FTP Ethernet cables (2) Eric, this 150 ohm story of STP cables sounds completely new to me. Also, my understanding is that both UTP and STP are used for 10bT ethernet. In the STP definition of IEEE802.3, there is no mention about different characteristic impedances from the required 100ohm of 10bT. Unfortunately I haven't yet received an answer to my original question as to how STP cables should be actually made (shielded twisted pairs vs overall shield) . As I already said in previous e-mails, the STP cables that I got look pretty much the same as FTP cables, that is they have just an overall shield (aluminum foil) around all wires. And they are all declared to be 100 ohms. Paolo At 16:56 06/09/2001 -0400, you wrote: Paolo, You may want to check if the FTP cable has a 100 Ohms characteristic impedance which would make it compatible with interfaces designed for UTP cable. STP cable is supposed to have a 150 Ohms impedance which is not compatible with standard 10baseT interfaces which are usually designed for UTP. Eric === Éric Meunier Hardware Architect E-mail: eric.meun...@ca.kontron.com mailto:emeun...@teknor.com Kontron Communication Inc. (Teknor) 616, rue Curé-Boivin Boisbriand, Québec Canada, J7G 2A7 Tel: 1-450-437-4661 ext. 2419 Fax: 1-450-437-8053 Web: http://www.teknor.com/ http://www.teknor.com
RE: STP vs FTP Ethernet cables (2)
hello: i am just curisous..how to measure shielding effectiveness of cables.. is shielding effectiveness of individual wire is better vs overall shield? is there any other ways to shield a cable? other than aluminium foil or conductive fabric around the cable? thank you in advance. Vijay Wani The Dow Chemical Company 433 Building Midland, MI 48667 Phone: 989-636-0473 Fax: 989-636-8785 Cell-phone: 517-859-0451 -Original Message- From: Allan, James [mailto:james_al...@milgo.com] Sent: Friday, September 07, 2001 9:04 AM To: 'Paolo Roncone' Cc: emc-p...@majordomo.ieee.org Subject: RE: STP vs FTP Ethernet cables (2) Paolo: Try this link to Quabbin wire company. It is a product selector guide with the types of wire used for different applications. All Ethernet applications are 100 ohm characteristic impedance and only have overall shields if shielded. Telecom cable (T1, DSL etc.) if shielded, are also 100 ohm but the shield (if present) is over the individual wire pairs with no overall shield. I find no reference to standard Ethernet cable at 150 ohms. LINK http://www.quabbin.com/finder/finder.cgi?cmd=app_form Jim Allan Manager, Engineering Services Nextira Solutions LLC 1619 N Harrison Parkway Sunrise, FL, 33323 E-mail james_al...@milgo.com Phone (954) 846-3720 Fax (954) 846-6282 -Original Message- From: Paolo Roncone [SMTP:pronc...@cisco.com] Sent: Friday, September 07, 2001 5:28 AM To: Meunier, Éric Cc: emc-p...@majordomo.ieee.org Subject: RE: STP vs FTP Ethernet cables (2) Eric, this 150 ohm story of STP cables sounds completely new to me. Also, my understanding is that both UTP and STP are used for 10bT ethernet. In the STP definition of IEEE802.3, there is no mention about different characteristic impedances from the required 100ohm of 10bT. Unfortunately I haven't yet received an answer to my original question as to how STP cables should be actually made (shielded twisted pairs vs overall shield) . As I already said in previous e-mails, the STP cables that I got look pretty much the same as FTP cables, that is they have just an overall shield (aluminum foil) around all wires. And they are all declared to be 100 ohms. Paolo At 16:56 06/09/2001 -0400, you wrote: Paolo, You may want to check if the FTP cable has a 100 Ohms characteristic impedance which would make it compatible with interfaces designed for UTP cable. STP cable is supposed to have a 150 Ohms impedance which is not compatible with standard 10baseT interfaces which are usually designed for UTP. Eric === Éric Meunier Hardware Architect E-mail: eric.meun...@ca.kontron.com mailto:emeun...@teknor.com Kontron Communication Inc. (Teknor) 616, rue Curé-Boivin Boisbriand, Québec Canada, J7G 2A7 Tel: 1-450-437-4661 ext. 2419 Fax: 1-450-437-8053 Web: http://www.teknor.com/ http://www.teknor.com/ -Original Message- From: Paolo Roncone [SMTP:pronc...@cisco.com] Sent: Thursday, September 06, 2001 4:18 AM To: Doug McKean Cc: EMC-PSTC Discussion Group Subject:Re: STP vs FTP Ethernet cables (2) 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
RE: STP vs FTP Ethernet cables (2)
Eric, this 150 ohm story of STP cables sounds completely new to me. Also, my understanding is that both UTP and STP are used for 10bT ethernet. In the STP definition of IEEE802.3, there is no mention about different characteristic impedances from the required 100ohm of 10bT. Unfortunately I haven't yet received an answer to my original question as to how STP cables should be actually made (shielded twisted pairs vs overall shield) . As I already said in previous e-mails, the STP cables that I got look pretty much the same as FTP cables, that is they have just an overall shield (aluminum foil) around all wires. And they are all declared to be 100 ohms. Paolo At 16:56 06/09/2001 -0400, you wrote: Paolo, You may want to check if the FTP cable has a 100 Ohms characteristic impedance which would make it compatible with interfaces designed for UTP cable. STP cable is supposed to have a 150 Ohms impedance which is not compatible with standard 10baseT interfaces which are usually designed for UTP. Eric === Éric Meunier Hardware Architect E-mail: eric.meun...@ca.kontron.com mailto:emeun...@teknor.com Kontron Communication Inc. (Teknor) 616, rue Curé-Boivin Boisbriand, Québec Canada, J7G 2A7 Tel: 1-450-437-4661 ext. 2419 Fax: 1-450-437-8053 Web: http://www.teknor.com http://www.teknor.com -Original Message- From: Paolo Roncone [SMTP:pronc...@cisco.com] Sent: Thursday, September 06, 2001 4:18 AM To: Doug McKean Cc: EMC-PSTC Discussion Group Subject:Re: STP vs FTP Ethernet cables (2) 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/ 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 Healddavehe...@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 mailto:pronc...@cisco.com phone: +39 039209 1538 fax: +39 039209 2036 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http
Re: STP vs FTP Ethernet cables (2)
I read in !emc-pstc that Meunier, Éric eric.meun...@ca.kontron.com wrote (in 5009AD9521A8D41198EE00805F85F18F0134036E@SEMBO111) about 'STP vs FTP Ethernet cables (2)', on Thu, 6 Sep 2001: You may want to check if the FTP cable has a 100 Ohms characteristic impedance which would make it compatible with interfaces designed for UTP cable. STP cable is supposed to have a 150 Ohms impedance which is not compatible with standard 10baseT interfaces which are usually designed for UTP. This is only likely to give any problems on long cable runs. 'Long' means several wavelengths of the highest useful frequency in the signal. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co..uk Eat mink and be dreary! --- 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 Healddavehe...@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.
Re: STP vs FTP Ethernet cables (2)
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 Healddavehe...@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.
Re: STP vs FTP Ethernet cables (2)
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 Healddavehe...@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.
STP vs FTP Ethernet cables (2)
This is a re-post with some corrections plus added some letters that got lost on the way from the .pdf file. Sorry for the inconvenience. Hi all, anybody out there can explain the difference between FTP (Foiled Twisted Pair) and STP (Shielded Twisted Pair) cables used for Ethernet links. In Ethernet standard IEEE 802.3 (2000) I find only a definition of STP (herebelow in copied and pasted from the standard - page 28): 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).Specifically for IEEE 802.3 100BASE-TX,150 ohm balanced inside cable with performance characteristics specified to 100 MHz (i.e.,performance to Class D link standards as per ISO/IEC 11801:1995).In addition to the requirements specified in ISO/IEC 11801:1995,IEEE 802.3 Clauses 23 and 25 provide additional perfor- mance requirements for 100BASE-T operation over STP. 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). Any inputs, suggestions etc. would be appreciated. Paolo --- 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
