Let us start with the inside of the cable, the extra one that is called the drain wire . Why is it there and what is it for ? This wire is there to help protect the wires within. You will find the drain wire is in mulit-conductor shielded cables. Since these are shielded then why have the drain wire ? The drain wire is woven within the shielding to help against surges with in the multiconductor wires. It takes the electrical surges and noises that can damage the internal conductors and drains them to ground. This wire will extend the life of the cable and keep your products safer . Secondly, what you have hooked up to this cable will be protected The drain wire is not in all shielded mult conductor cables, so if you have an application where there could be possible electrical surges at times or harmful noises I suggest you get a cable with a drain wire.