Keyed and Unkeyed Jacks
Brian Dorn
What is the difference between a Keyed Jack and an UnKeyed Jack?
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Brian Dorn <><><><><>**<><><><><> bd...@navix.net
<> http://www.geocities.com/SiliconValley/3105 <>
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RoBaer Stewart
Lets assume you are refering to RJ styled plugs (ie rj11 or 12 is the type
used by ma bell in most houses across north america... psuedo named 'a
phone jack'.) It has 4 wires (6 in the case of the rj12) CAT 5 wiring
standards for ethernet cards when using the 'twisted pair' option will be
an RJ45 jack. it has 8 wires, so a little wider than a normal phone plug.
Ethernet only needs 4 wires out of the 8 to work, but thats another
story...
A keyed RJ jack looks identical to a non-keyed jack, excpet it has a little
plastic tab on one side to make sure that the jack only goes in one
direction. A keyed rj jack can not plug into a non-keyed rj jack without
wiping out your exacto knife and shaving it off.
ie: RJ45 (nonkeyed) RJ45(keyed) (when looked at end, wire
side up)
12345678 12345678
------------- -------------
|------------| |------------|
|------------| |------------|==
[___] [___]
The most practical use for a keyed jack is when the cable has unique wire
switching and you need to ensure that one end only can plug into the wall.
(ie say your ethernet card uses lines 1,2,3 and 6. If you wire that
directly through a ribbon cable, it would come out 1,2,3 and 6 on the other
end.... BUT when you are sending data over long distances, you want to use
twisted pair and send signals down common pairs of lines to reduce signal
loss.... so you want the other end to come out 1,2,3 and 4 (not 6) to use
the first 2 pairs of wiring. By using a keyed plug on this end, and
terminating your twisted pair wire with keyed plugs, you ensure that noone
will accidently switch the cable around, losing the ability to connect to
the network. (there are other reasons and uses, and ways around this, but
that is keyed plugs in a nut shell.)
Another flavour of RJ jack that is similar to keying, is the MMJ jack.
Instead of a little tab that sticks out, it has the right side of the plug
end thicker than the left and that little clip is offset as opposed to
being in the middle. This jack is common in man DEC vt terminals, but
seldom seen in the PC world. (when viewed as the jacks above)
Probally more than you wanted... but hope it helps.
RoBaer
Brian Dorn <bd...@navix.net> wrote in article
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