Siemens SIMATIC NET PROFIBUS - Manual (Page 33)

Topologies of SIMATIC NET PROFIBUS Networks
2-7
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
PROFIBUS Optical Bus Terminal (OBT)
Using a PROFIBUS optical bus terminal (OBT), an individual PROFIBUS node
without an integrated FO port or a PROFIBUS RS-485 segment can be attached to
the optical PROFIBUS network (see Figure 2-2 ).
The attachment is made to the RS-485 interface of the OBT using a PROFIBUS
cable or a preassembled connecting cable. The OBT is included in the optical
PROFIBUS bus via the FO interface.
2.2.2 Topologies with OLMs
OLMs
The OLMs have a floating electrical channel (similar to the channels on a repeater)
and depending on the version, they have one or two optical channels.
The OLMs are suitable for transmission rates of 9.6 Kbps to 12 Mbps. The
transmission rate is detected automatically.