I've always used the 'STRIPE' side as 'SIGNAL'. This is pretty consistent with a lot of product. Likewise, you will find that there is a raised rib on one of the pieces of cable when it is a dual cable. The ribbed edge is typically the negative. If you have a zip power cord at home, there is almost always a smooth edge wire and a ribbed edge wire and the ribbed edge is the neutral while the smooth edge is the hot. The hot is almost always the one with writing on it.