Operating instructions

Guidelines for Installing Networked Automation Systems in Buildings
7-13
SIMATIC NET Twisted-Pair and Fiber-Optic Networks
C79000-G8976-C125-02
7.3.4 Shielding Devices and Cables
Shielding Cables
The high degree of noise immunity of SIMATIC NET twisted pair copper networks
is achieved by the exclusive use of shielded twisted-pair cables. The highly
symmetrical twisted signal wires are surrounded by a combination of foil and
braided mesh shields. The shield makes large-area, conductive contact with the
casing of the attached DTE or network component at both ends of the twisted-pair
cable via the connector/outlet. The entire communications electronics, consisting of
transmitter and receiver chips as well as the signal cables is protected from
electromagnetic influence from the outside world by a closed “cocoon” of
electrically conductive device casing and cable shield.
Note
The values specified for noise emission and noise immunity in the technical
specifications of all SIMATIC NET Industrial Ethernet components assumes the
use of shielded twisted-pair cables.
As explained in the installation rules for the devices, the shields of the twisted-pair
cables must make good conductive contact with the device casing at both ends.
This is ensured by the SIMATIC NET connectors designed specially to match the
devices.
If, on the other hand, the rules are ignored and unshielded cables are used or the
shields do not make contact with the casing at both ends, there is no longer any
guarantee that the technical data regarding noise emission and noise immunity will
be adhered to. In this case, the operators of the system must take responsibility
themselves for compliance with the legal limit values for noise emission and noise
immunity (CE mark)!