Post by thread:Network cat5 cabling question

part 0 417 bytes If you get this mail, our network is working! (100M) -Wendall -----Original Message----- From: john pearson [SMTP:spam_OUTxeroTakeThisOuTCWIA.COM] Sent: Monday, May 11, 1998 6:26 PM To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU Subject: OT: Network cat5 cabling question Thank you for reading Is it ok to run 15 to 20 cat5 network cables through about 6' of metal conduit (1-1/4" emt). I hope this is enough info. Thank you John

Chris Eddy wrote: > Yes, you are safe. Cat 5 and other twisted types (twisted pair, not > mentally) are reasonably good at keeping signals to themselves. Think > of phone lines on the pole. I'd take this all with a "grain of salt". Six feet, you should get away with it. Some longer distance, maybe fifty feet, you may well strike problems. I'm not actually sure what is meant by "cat 5". If it refers to shielded lines, no complaints at all. If it refers to 10BaseT cabling using 4 out of an 8-wire cable, then there is a trick as this is *not* in fact twisted pair. Telephone lines on the pole *are* twisted pair as they are carefully balanced by regular swapping of individual pairs in a pattern (Gray code variant - it's abit of a subject in itself); it it to *this* that the "twist" refers. Pairs in a composite cable are actually twisted at different pitches. It's all about balancing out "crosstalk". The flat "strap" cable used with "RJ" connectors is not twisted pair, and is *not* designed as such to avoid crosstalk. Randomly and separately pulled through a duct with other like cables, it may act "twisted", but if the straps are accidentally or deliberately laid neatly together for any distance you really are "asking for" crosstalk problems. This is of course exactly what Chris goes on to describe. Cheers, Paul B.

On Tue, 12 May 1998 22:17:39 -0000 Eric Smith <ericKILLspamBROUHAHA.COM> writes: > >Note that flat modular telephone cable is often wired with a flip >(i.e., >pin 1 at one end is wired to pin 'n' at the other end. 10BaseT and >100BaseT >cable has to be "straight-through", unless you're using a crossover >cable >between two nodes, in which case two pairs get swapped. > > Anyone know why telephone line cords are assembled with a "flip"? Actually, the flip SEEMS like it'd be a great idea for data cables. All sockets would be wired the same. The swapping of transmit and receive pairs would happen in the cable flip. You could hook anything to anything (eliminating the old RS232 DTE/DCE problem). Harold _____________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call Juno at (800) 654-JUNO [654-5866]

Actually, the flip SEEMS like it'd be a great idea for data cables. All sockets would be wired the same. The swapping of transmit and receive pairs would happen in the cable flip. You could hook anything to anything (eliminating the old RS232 DTE/DCE problem). The last round of "rs232 on rj45" pinouts developed at cisco had exactly this feature. You could plug one end of a (flipped) rj45 flat cable into one jack and the other end into another jack, and the right wires would be connected so that everything (data, hw flow control, modem control) worked right. In addition, the "important" wires were in the middle, so you could use as small as 4-wire cable for a 3-signal circuit. I thought it was a great idea. It generated quite a bit of complaint and confusion however... 1) Using "standard" wiring schemes, it apparently results in inappropriate wires being twisted with each other once you get to the twistewd part of the wiring. 2) While we based this and the db25 adaptors on an existing (flipped) rj-45 cable assuming that they were "standard", they weren't. At least one entire product line that uses the same pinout for the rj45 jacks for the "console" and "auxilliary" somehow missed something and shipped (for a LONG time) with NON-flipped flat cables, and their own (different) rj45-db25 adaptors. Really confusing things happened if you tried to move connectors or cables from those products to or from the "terminal server" products that understood the original pinout. 3) Things get confusing when you try to chain cables together... BillW cisco