Construction

2 cores, twisted, with common shield

Conductor cross section

> 0.22 mm² (24 AWG)

Twisting rate

> 10 per meter (symmetrically twisted)

Core insulation

Polyethylene (PE)

Resistance per core

< 100 Ω/km

Characteristic impedance

ca. 120 Ω (100 Ω ... 150 Ω)

Capacitance between the cores

< 55 nF/km (if higher, the max. bus length must be reduced)

Terminating resistors

120 Ω ¼ W at both line ends

Remarks

Commonly used telephone cables with PE insulation and a core diameter of  > 0.8 mm are usually sufficient.

Cables with PVC core insulation and core diameter of 0.8 mm can be used up to a length of approx. 250 m. In this case, the bus terminating resistor is approx. 100 Ω.