Canare Star Quad - what's the fourth wire for??

[boojum]

OK, Canare Star Quad is quite popular for interconnects.  One ground, one positive and one negative and the fourth wire is???  I am stumped as the terminators are for three connections. 
Thanks

[boojum]

I put blue together, white together, and use the shield for ground.

Mike, OK, but then what's the point of four wires if you are only going to use two??  What am I missing here?  And with the standard three wire setup is the shielding hooked to the ground wire??

[JD]

I put blue together, white together, and use the shield for ground.

Mike, OK, but then what's the point of four wires if you are only going to use two??  What am I missing here?  And with the standard three wire setup is the shielding hooked to the ground wire??

I think the reasoning for using the four wires grouped into two pairs, is that the way the pairs of wires are twisted together internally, it helps to cancel out transient noises that get past the shielding.


Edit to add: I do a lot of industrial control wiring at my work. Groups of twisted pairs are often used to minimize the "bleeding" or crosstalk of signal from conductor to conductor when wires are run parrallel to each other. It is also pretty common that the twist rate per inch is different on each pair within a cable.
Not sure how this translates over to our use of these cables? 

[twatts]

2x pairs of twisted cables, helps reduce interference:

http://en.wikipedia.org/wiki/Twisted_Pair

Terry

[boojum]

2x pairs of twisted cables, helps reduce interference:

http://en.wikipedia.org/wiki/Twisted_Pair

Terry

Terry - OK!  Followed the link to XLR and all.  Very informative.  Never would have guessed two pair would reduce inerference.  Thanks, all.  Now, I have to order the cable and connectors and start smelling the rosin again.