osh@jhereg.osa.com (John M. O'Shaughnessy) (04/16/91)
10Base-T is a wiring standard for Ethernet over twisted pair. It requires 2 pairs of wire, one for transmit and one for receive. There are other, non 10BaseT wiring methods out there, some using two pairs, some using one pair. If you are thinking of wiring up a new network, I'd stick with the 10Base-T standard. John -- John M. O'Shaughnessy osh@osa.com Open Systems Architects, Inc. Minneapolis, MN
jbreeden@netcom.COM (John Breeden) (04/17/91)
In article <1991Apr8.135731.2901@eng.umd.edu> naiming@eng.umd.edu (Naiming Shen) writes: > >I was told by a salesman that Twisted Pair scheme is different than >the 10BaseT. He said 10BaseT uses 2 pairs of wires, while Twisted Pair >uses only one pair of wires and a converter can be added to this twisted >pair so that thin net cable can be connected to the converter. It sounds >great for the Twisted Pair scheme(only one pair of wires, thin wire can >be added), I am wondoring if there is any shortcomings? > Your *salesman* needs to go back to school..... Twisted pair is WIRE and 10baseT runs on twisted pair (2 pairs rx and tx). BTW, the two pairs defined in the standard (pair 1&2 and pair 3&6) are defined as data pairs in the AT&T Premise Distribution Spec (what 10baseT's wiring is based on and also where the RJ45 comes from). The remaining two pairs are for phone or ISDN (both ISDN and PBXs use 4,5,7,8 as the two voice pairs). What your *salesman* is referring to is a twisted pair balun (3Com makes one called the PairTamer). The advantage? Real Cheep and only uses 1 pair. Disadvantage? NOT a standard (10baseT specifically outlaws baluns (passive device) and calls for repeaters - a 10baseT hub is a multiport repeater - an active device). Baluns are passive devices, prone to noise and jitter (compaired to 10baseT) and are propriatory (ie: not defined by any standards body). The *standard* PDS twisted pair wire pulled to the desktop is 4 pair twisted. What your *salesman* SHOULD have said is there are a *number* of ways to run ethernet over twisted pair, 10baseT (an IEEE standard), baluns (ala PairTamers) and propriatary protocols used before the 10baseT standards (ie: Synoptic's Lattisnet, Cabletron and David System's old protocols etc). 10baseT is installed today more than any other medium in large nets because it's a standard (ie: You can mix and match different vendors based on best price/performance/features) is more reliable (10baseT hubs jam bad ports, are active repeaters and compensate for jitter on the receive end) and is easier to manage (the many different vendor MAC level hub "management" "features" built into products). -- John Robert Breeden, jbreeden@netcom.com, apple!netcom!jbreeden, ATTMAIL:!jbreeden ------------------------------------------------------------------- "The nice thing about standards is that you have so many to choose from. If you don't like any of them, you just wait for next year's model."
les@chinet.chi.il.us (Leslie Mikesell) (04/22/91)
In article <1991Apr16.175210.5468@netcom.COM> jbreeden@netcom.COM (John Breeden) writes: >BTW, the two pairs >defined in the standard (pair 1&2 and pair 3&6) are defined as data >pairs in the AT&T Premise Distribution Spec (what 10baseT's wiring is >based on and also where the RJ45 comes from). The remaining two pairs >are for phone or ISDN (both ISDN and PBXs use 4,5,7,8 as the two voice pairs). Is there a quickref for this scheme available somewhere? Is there a standard part to split the data and voice parts out of a wall-jack RJ45 into a separate phone RJ45 and 10baseT RJ45 or do you have to hand-wire something to do this? What about the phones that draw power from the System 75? I'm considering replacing some daisy-chained 1M starlan runs with 10baseT and it would be a big win if we don't have to add any wiring for the extra hub-to-desktop runs. Les Mikesell les@chinet.chi.il.us
jmw@brahms.amd.com (Mike Wincn) (04/26/91)
In article <1991Apr8.135731.2901@eng.umd.edu> naiming@eng.umd.edu (Naiming Shen) writes:
<I was told by a salesman that Twisted Pair scheme is different than
<the 10BaseT. He said 10BaseT uses 2 pairs of wires, while Twisted Pair
<uses only one pair of wires and a converter can be added to this twisted
<pair so that thin net cable can be connected to the converter. It sounds
<great for the Twisted Pair scheme(only one pair of wires, thin wire can
<be added), I am wondoring if there is any shortcomings?
Where in the world did you hear of this, and can you provide
any more details?
--
Mike Wincn jmw@brahms.AMD.COM
(408) 749-3156 DISCLAIMER: I speak for myself unless noted otherwise.