Siemens SIMATIC NET OLM12M Description And Operating Manual page 69

6ZB5530–3AB00–0BA0/01
6.6 Setting the Terminating Resistors for Channel 1
The switch for setting the terminating resistors (termination) is located on the front panel of the
OLM12M.
Set both switches to the 'on' setting
- If the connecting cable between the optical link module OLM12M and the DTE is longer than 5
meters. (In this case, the connecting cable must also be terminated on the DTE.)
- When the OLM12M is at the start or end of an RS 485 bus segment.
Figure 15: Activating the Terminating Resistors
In all other situations, set both switches to 'off'.
(default)
Figure 16: Deactivating the Terminating Resistors
Note that both switches must always be in the same position!
Different settings for the two switches can lead to disturbed transmission.
Set the switches using a pointed object.
Figure 17 shows the inner circuits of the RS 485 interface.
Figure 17: Activating Terminating Resistors on Channel 1
Copyright Siemens AG 1997
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SIMATIC NET OLM12M