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Siemens TX-I/O Engineering and installation guide CM110562en_13
Building Technologies Principles of electrical design 2019-05-15
10.6.4 Island bus expansion cable material
Cable specifications for
island bus expansion
The cables must meet the following specifications:
• Shielded cable (foil or mesh)
• Capacitance between wires + and – <50 pF/m
• Wave resistance between wires + and – 100...120 Ohm
• Specific resistance for wires + and – <100 Ohm/km
(AWG24 or thicker)
The following cable types normally suit the requirements for island bus expansion.
However, always check if the above specifications are fulfilled!
– RS422 / RS485
(almost all cables are suitable)
– Ethernet CAT 5, CAT 6, or CAT 7
(cables for Power over Ethernet; other cables have insufficient copper cross section.
• Bedea
Type 3197, S/STP, CAT7+, 43 pF/m, 100 Ohm, <=80 Ohm/km (AWG23)
Type 2374, S/STP, CAT7, 43 pF/m, 100 Ohm, <=80 Ohm/km (AWG23)
Type 2279, S/STP, CAT6, 43 pF/m, 100 Ohm, <=80 Ohm/km (AWG23)
Type 2103, S/UTP, CAT5, 48 pF/m, 100 Ohm, <=94 Ohm/km (AWG24)
Type 2102, F/UTP, CAT5, 48 pF/m, 100 Ohm, <=95 Ohm/km (AWG24)
• Belden
Type 9841, for RS-485, 42 pF/m, 120 Ohm, 79 Ohm/km (AWG24)
Type 9729, for RS-422, 41 pF/m, 100 Ohm, 79 Ohm/km (AWG24)
Type 8102, for RS-422, 41 pF/m, 100 Ohm, 79 Ohm/km (AWG24)
Type 3084A, for DeviceNet, 39 pF/m, 120 Ohm, 92 Ohm/km (AWG24)
Cable types
Examples