Siemens SIMATIC TIWAY 1 - Manual (Page 82)

THE TIWAY I NETWORK PORTS
UNILINK HOST ADAPTER 4-8
USER MANUAL
4.2 REDUNDANT MEDIA TRANSMISSION
Most TIWAY I conformant devices support a redundant media scheme which
provides active access to a device over one of two independent media channels.
Should access to a device fail on one channel, communications can be
automatically or manually switched to the alternate channel. This type of a
circuit is illustrated in Figure 4–5. Examples of the software commands are
given in Chapter 2.
UNILINK
Drop Cables
Up to 254
Secondaries
Secondary Bus
(alternate trunk)
Bus
(main trunk)
Figure 4–5 Redundant Media Circuit
NOTE
Redundant media is provided to improve a network’s
mission reliability. However, the adapter cannot use
the dual media ports to access two independent
networks.