Shahriar,
The cable you have looks like a balanced cable, which would have a positive signal on one lead and a negative on the other, while the shield holds the ground. But, your cable is not balanced because the wires do not have the same number of strands. Because of this, you do not have the same potential from gound on both cables (balance). Unbalanced cable such as coax has one center wire and the shield acts as the ground. The cable you have is unbalanced cable, but has an advantage. The 3 wire conductor should be used as the ground. Thus, the ground is split between the shield and the 3 wire conductor. This will give you a little more help with noise rejection. A cable which uses only the shield as the ground tends to allow noise with movement of the cable. Even more so when the shielding starts to wear and fray internally. In your cable, this will not be so apparent.
This cable would not work in a system which requires a balanced signal. Both leads would need to deliver the same strength of signal (with opposite polarities). The difference in the number of strands would cause long cables to become unbalanced. However, in an unbalanced application, this is excellent cable.
MP
