Product specifications

Troubleshooting
9-22
SIMATIC 545/555/575 System Manual
Checking RS-485 (Twisted Pair) Cable Installation (continued)
Line-to-line resistance that is above the maximum specified in Table 9-6
may be caused by the following:
• Incorrect termination resistors are installed.
• Fewer than two termination resistors are installed: always use at least
one termination resistor, even with the simplest installation.
• The cable is open between the point of measurement and one or both of
the termination resistors.
Resistance above
Maximum