Cables are mostly round. This has always been the case and with good reason. Round cables are particularly easy to route, and the channels can be sealed without difficulty. So why is the cable of the supposedly simplest fieldbus system in the world flatand also has a mechanically coded profile? Because the typical yellow ASi cable is the key to the simplicity of AS-Interface. The unshielded, two-conductor cable not only transmits data and power, it also enables easy and cost-effective installation of ASi or ASi-5 in the field. Thanks to piercing technology, field devices can easily be installed on the mechanically coded (thus reverse polarity protected) ASi cable – with perfect contact and while still achieving protection class IP67.