Re: [SLUG] Re: [ot] Using telephone wiring for networking?
On Wednesday 07 December 2005 11:44, [EMAIL PROTECTED] wrote: On Tue, 2005-12-06 at 10:41 +1100, James Gray wrote: I've personally seen what happens to a thin-ether (10base2) network when a PC's power supply decided to send all 240VAC through the motherboard and hence the network card. Goodnight Irene for everything else too. However, the same machine had an AUSTel certified internal (ISA) modem - the PABX it was running through was untouched. U ... when an elderly and distinguished scientist says something is impossible he's nearly always wrong ... A nic card has an isolating transformer rated to some 1000v between it and the cable. For the 240v to escape A it needs a faulty transformer on A, then to infect B it needs another faulty transformer on B (Sorry if I've screwed up the quoting - big snippage). I know. I'm not trying to explain it. The year was 1995, the place, MGM Grand Casino Darwin (NT, Aust.). The result was about 15 machines on the particular thin-ether segment got their NIC's completely fried and about 4 (maybe 5) machines on the segment also lost other internal things, like motherboards or PSU's. Obviously the machines with dead motherboards etc had faulty isolation transformers - they were cheap NIC's anyway (SMC rebadged jobs IIRC). They (MGM) were in the process of rolling out CAT3 STP to replace the thin ether (the data cabling company I worked for at the time had the contract). The faulty cards caused the PHB's to rethink their get the cheapest NIC's and be happy mentality and they lashed out on 3Com cards after that. Not that it stopped people plugging their Ethernet (RJ45) NIC's into the PABX sockets (also RJ45...but RED) - POP, time for another NIC. Strangely, after all the cable had been run for the CAT3 and PABX, they offered me a job in their IT department. I accepted on the condition I never had to crawl through another tiny hole in a ceiling or floor cavity...the deal was done :P Cheers, James -- Anyone can hold the helm when the sea is calm. -- Publius Syrus -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
RE: [SLUG] Re: [ot] Using telephone wiring for networking?
I thought so too, until I tested* some supposedly 1500V transformers of the type used in NICs and found that they broke down at voltages a lot lower than 1500V (I think the lowest was 500V). Unless they are tested (and certified so), they may survive or they may emit smoke. Needless to say I rejected the batch. Now a faulty switch mode power supply could potentially put a lot more than 240V onto the low voltage output, as they switch at a much higher voltage internally, like 400 or 600 V. That would break down an uncertified NIC. Kaboom. - Jill. * that was at Scitec many years ago. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Wednesday, 7 December 2005 11:45 AM To: slug@slug.org.au Subject: [SLUG] Re: [ot] Using telephone wiring for networking? On Wednesday 07 December 2005 07:58, [EMAIL PROTECTED] wrote: On Tuesday 06 December 2005 13:35, Robert Collins wrote: On Tue, 2005-12-06 at 10:41 +1100, James Gray wrote: AIUI austel certification only kicks in if you are connecting the thing to the phone network. If you happen to have a bunch of copper in the walls, that is not connected to the public network - it does not apply. And by connected to the public network they mean in any way through any device. So even if you isolate your network from the public one with a router or modem etc, you're still deemed to be connected. Not sure if you're still deemed to be connected if the external/public link is wireless though (they are more concerned about electrical isolation than spurious data). At tleast this was how the regs were written back in '95 when I was AUSTel Certified. Things may have changed - usual disclaimers apply. Jesus thats scarey. Why isn't my power socket AUSTel certified ? Because the assumption is that you are using AUSTel approved network/telephone equipment which has been certified to meet the isolation requirements. I've personally seen what happens to a thin-ether (10base2) network when a PC's power supply decided to send all 240VAC through the motherboard and hence the network card. Goodnight Irene for everything else too. However, the same machine had an AUSTel certified internal (ISA) modem - the PABX it was running through was untouched. See the difference? U ... when an elderly and distinguished scientist says something is impossible he's nearly always wrong ... A nic card has an isolating transformer rated to some 1000v between it and the cable. For the 240v to escape A it needs a faulty transformer on A, then to infect B it needs another faulty transformer on B James -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
