[asterisk-users] Crossover cable for E1 ?

[Kevin P. Fleming]

On 01/24/2011 06:54 AM, A J Stiles wrote:
> On Monday 24 Jan 2011, Tilghman Lesher wrote:
>> On Monday 24 January 2011 03:46:18 A J Stiles wrote:
>>> white/blue blue white/green orange white/orange green white/brown brown
>>
>> This is incorrect.  The pairs should be:
>>
>> blue white/blue white/green white/orange orange green white/brown brown
>>
>> Wire 1 MUST swap with 4 and Wire 2 MUST swap with 5.  To do as you have
>> shown above switches the polarity on each electrical circuit.  It is
>> especially important that you do not switch the polarity, as some equipment
>> does not auto-correct for reversed polarity.
>
> I stand corrected -- though, the arrangement I described has definitely worked
> for me in the past  (I'm looking right now at a homebrew crossover cable I
> replaced with a longer one when we installed a new server),  so maybe our
> WCT410P is just more forgiving than some kit out there?
>
> Anyway, Tilghman is the expert, I'm just a satisfied user :)

T1, E1 and BRI links on copper cables use differential signaling, and 
thus there is no 'polarity' to be concerned about. This is not true for 
analog links, though, where polarity can be important (although most 
equipment is designed to auto-correct if the polarity of Tip and Ring 
are not preserved).

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kfleming at digium.com
Check us out at www.digium.com & www.asterisk.org