Looking at the spec, CAT 5 has a lower impeadance than CAT 3 by reason of it having more twists per inch The reason that 100mb can work on CAT3 is more by chance than design as at that speed the cable tends to pick up outside interference from electrical wiring and other sources of RFI due an impeadance mismatch. Since the average cable is terminated 6 times before it gets from one end to the other I have been using patch cables without any cross connects. The major failpoint of CAT 3 or 5 cable is at the connectors not in the cabling itself. At every connector the twist in the cable is interupted, introducing a mismatch in the cable impeadance and deminishing the max bit rate. The NIC can compensate for this by adjusting it's impeadance matching to the cable but this is "fix" rather that a solution. It is worth mentioning that both these CAT's are unshielded and not much better than standard telephone cable, for spectacular and dependable data speeds COAX cable has very high data through-put and Fiber optic (with its immunity to RFI) can blow the "barn doors" off anything. As for PoE working on CAT 3 it depends.. CAT 3 had two specs with regards to the RJ21 connectors and the pin-outs. The more common spec is the same as CAT 5 but some cables are wired differently and effect the PoE cable pair.
TTFN Merry Christmas Henry < Drew Gibson> > I can't imagine why PoE WOULDN'T work on Cat3 cable, the pinout and > colour coding is the same as Cat 5 and I doubt there is any high speed > signalling for the PoE negotiation. It is just the wire gauge and number > of twists that change. Cat3 was designed to run 10Mb ethernet but 100Mb > is dodgy. Also note that plain Cat5 was designed for Gigabit, it's just > that 5e is more reliable at high speeds on longer runs. > > Is the obstacle to using Cat3 more in the sales commission of the cable > contractors than in any inherent physical property of the cable? > > regards, > > Drew > > > > Jim Van Meggelen wrote: >> For a long time now the common wisdom is that a big obstacle to re-using >> Cat3 cabling for VoIP phones is that PoE is not supported on Cat3. >> >> This article would seem to disgreee: >> >> http://en.wikipedia.org/wiki/Power_over_Ethernet >> >> Comments? Opinions? Experiences? >> >> Thanks, >> >> Jim >> >> >> -- >> Jim Van Meggelen >> Core Telecom Innovations >> [EMAIL PROTECTED] >> www.coretel.ca >> 416-425-6111 x6001 >> 877-CORETEL x6001 (Canada) >> www.oreillynet.com/pub/au/2177 >> http://downloads.oreilly.com/books/9780596510480.pdf >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: [EMAIL PROTECTED] >> For additional commands, e-mail: [EMAIL PROTECTED] >> >> >> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > > -- Henry --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
