Siemens SIMATIC NET PROFIBUS - Manual (Page 168)

Active Components for RS-485 Networks
5-2
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
5.1 RS-485 Repeater
What is an RS-485 Repeater?
An RS-485 repeater amplifies data signals on bus cables and links bus segments.
Using the RS-485 Repeater (6ES7 972-0AA01-0XA0)
You require an RS-485 repeater in the following situations:
S When there are more than 32 stations (including repeaters) connected to the
bus
S When electrically isolated bus segments are required or
S When the maximum cable length of a segment is exceeded (see Chapter 3
“Network Configuration”).
Rules
If you want to install a PROFIBUS network with RS-485 repeaters, you can
connect a maximum of nine RS-485 repeaters in series.
Design of the RS-485 Repeater
Table 5-1 shows the elements of the RS-485 repeater.