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Friday, September 14, 2012

Cat 5 Cabling Mnemonic-a few....
( I figured I'da Swipe this cause it's offten so easy to forget the B cabling order. )

Cat 5 Cabling Mnemonic

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I don't have to make Ethernet cables or punchdowns very often -- perhaps once a month, at most.  Something that has always bugged me is that every time I made a cable, I had to look up the T568A or T568B wiring standard to remember the termination order.

I remembered the basics.  Unpowered cat 5 uses pins 1 and 2 for transmit, and pins 3 and 6 for receive.  I knew that (white/)blue and (white/)brown never changed their pin numbers. A straight cable is always "A" to "A", or "B" to "B", while a crossover is always "A" to "B".

But for whatever reason, I could never remember the exact color order for the wires, and certainly could never remember which colors are swapped between T568A and T568B.

So I made a mnemonic.  There are a few cat 5 mnemonics on the web, but they mostly seemed like rote memorization rather than utilizing the power of a true mnemonic: a mnemonic is catchy.

So here it is:

"A" is for "apples", that always start green.
"B" is for "bees", that like tangerines.
Whites always come first, except is it's blue.
Brown always comes last, the color of poo.

This works (for me, anyway), but it requires some fundamental understanding of the wiring standard, and how Ethernet uses it.  I think this is fine, since if you don't understand the fundamentals, you shouldn't be terminating cable in the first place.
Blue - The Sky is Blue
Orange - the Sun is orange on the horizon
Green - on the Horizon there is trees
Brown - The Trees are in Dirt.

shrug.. seems to work - that's for A though.. B you just flip orange and green.


and my favorite:


I like that one because it has 2 of the colors in the saying and its funny and easy to remember!!

arrange to
wig the
Who blames
when brow

(Improvements welcome.)

USOC (Universal Service Order Code)

                   8-pins  6-pins
                        |  |
      /-------------T4  1     White/Brown
     /    /---------T3  2  1  White/Green
    /    /    /-----T2  3  2  White/Orange
   /    /    /    /-R1  4  3  Blue
pr4\ pr3\ pr2\ pr1\-T1  5  4  White/Blue
    \    \    \-----R2  6  5  Orange
     \    \---------R3  7  6  Green
      \-------------R4  8     Brown