[asterisk-users] Crossover cable for E1 ?

[A J Stiles]

On Saturday 22 Jan 2011, Tim Panton wrote:
> I'm looking to connect a BMC 450 to an asterisk with a Digium Quad E1 card.
>
> Am I right in thinking that I'll need a special 'crossover-E1' RJ45 cable?
>
> If so, any clues where I might buy one in the UK? The Digium card sellers
> don't seem to stock such a thing.

It's easy to make an ISDN crossover cable.

Cut one end of a standard network cable.  Get a new RJ45 plug, rubber boot  
(not strictly necessary, but makes it look neater)  and crimping tool.  Push 
the rubber boot onto the end of the cable first.  Strip about 2cm. of outer 
sheath and separate the inner pairs, then arrange in this order from left to 
right with the brass contacts uppermost:

white/blue blue white/green orange white/orange green white/brown brown

(i.e., wrap the "green" pair around the "orange" pair).  Now trim the wires so 
there is just over 1cm. protruding from the outer sheath.  Insert the wires 
into the new plug, crimp, and pull the rubber boot down over the plug.

If you have an AVO, test for continuity as follows: pin 1 to pin 5, pin 2 to 
pin 4, pin 4 to pin 2, pin 5 to pin 1.  (Pins 3, 6, 7 and 8 are not used in 
this configuration.)  

Finally, as this cable is a special one, BE SURE TO LABEL IT to prevent 
mistakes.  

For completeness' sake I ought to say, if you want or need to crimp the other 
end yourself, the wires should be arranged as follows:

white/orange orange white/green blue white/blue green white/brown brown

You did push the rubber boot on the end before you crimped the plug, didn't 
you?


-- 
AJS

Answers come *after* questions.