Fieldbus is an all-digital, serial, two-way communications protocol (HS1)that standardizes the interconnection of field devices at a communications rate of 31.25 kB/s. The field devices are made accessible to communication networks (running at 1 or 2.5 Mb/s), through use of linking devices. Because a simple twisted pair of wires can carry the signals between the field devices and the networks, Fieldbus users can reduce the amount of I/O and control equipment (due to distribution of control into the field devices), plus they can use fewer intrinsically safe (IS) barriers, cabinets, cables and connectors.
And, since the pair wire can support multiple functions within a single device (such as diagnostics, control and auto error correction), the twisted pair cable becomes the integral part of a more efficient, more reliable, and more cost-effective industrial control system.
Fieldbus cables are classified as followings : - Size : 0.32 sq.mm (22 AWG) , 0.8 sq.mm (18 AWG) , 1.25 sq.mm (16 AWG) - No. of cores/Pairs : one or more -Conductor material : Plain or tinned copper -Conductor type : Solid (Class1)/Stranded(class2)/Fine stranded (Class 5) - Round -Insulation: Cross-linked polyethylene (XLPE) , polyethylene (PE) or foam polyethylene ( FPE) -Pair screens: Laminated screening tape comprise of aluminum bonded to polyester plus one or more tinned annealed copper wires applied over each pair. (If required.) -Collective screen : Laminated screening tape comprise of aluminum bonded to polyester plus one or more tinned annealed copper wires applied over the screened pairs or laid up cores. (If required.) -Inner sheath: Polyvinyl chloride (PVC) or polyethylene ( PE) -Metallic sheath : Lead sheath -Separation sheath: Polyvinyl chloride (PVC) or polyethylene ( PE) -Outer sheath: Polyvinyl chloride (PVC) or Polyethylene (PE) Other features : -Ultra violet (UV) resistant colored outer sheath -Low smoke and fume (LSF) -Halogen free and flame retardant (HFFR) -Oil & hydrocarbon resistant -Fire resistant -Vermin proof
Construction features:
-Armour: Galvanized steel wire, tape or braided armour 
