Siemens 500 NIM - Manual (Page 122)

PM550 CIM Requirements A-5 SIMATIC TIWAY I Series 500 NIM User Manual
2. If more than one CIM is attached to a Local Line, place CIMs at the
extreme ends of the Local Line trunk. Install the jumpers provided
with the outermost CIMs in accordance with the instructions in the
PM550 CIM User’s Manual, Manual Number PM550–1101154–4. This
will apply the correct bias to the Local Line to prevent oscillations of
the CIM receivers.
To terminate the Local Line, replace the existing terminating resistors
inside the outermost CIM tap housings with 150-ohm resistors between
the LLM+ and the cable shield, and also between LLM– and the cable
shield. This resistance value is 150 ohms in each instance, and the
connection is in accordance with instructions inside the tap housing.
The combination of termination resistors in the CIM together with
these 150-ohm resistors, provides the correct Local Line termination.
Figure A-1 illustrates the proper placement of the CIMs and the
termination resistors for networks having CIMs and NIMs without the Bias
Switch.
TIWAY I
PRIMARY
TERMINATING RESISTOR(150 ohms)
INSTALLEDNOT INSTALLED
T-TAP T-TAP
NOT INSTALLED INSTALLED
T-TAP T-TAP
TERMINATING RESISTOR(150 ohms)
T-TAP
CIM
PM550
JUMPERS
INSTALLED
SELECTED
CIM
NOT SELECTED
BIAS
CIM
JUMPERS
INSTALLED
NOT SELECTED
CIM
PM550
SELECTED
BIAS
NIM's: BIAS OFF
CIM's: JUMPERS OFF
Figure A-1 Local Line Bias and Termination