ABB AC 900F Mounting And Installation Instructions Manual page 47

Section 3 Modules
CAN single AC 900F at the beginning of the bus_us.png
Redundant AC 900F controller at the beginning (end) of the CAN Bus
The terminating resistors integrated into the TP 910F termination plug ensure that
the termination and, thus, the function of the three CAN Bus lines is preserved even
if a CAN bus module or controller is replaced. TB 870F is used for connecting the
CAN bus between controllers and to the I/O rack.
The TK 831F cable contains feed and return lines. When replacing a CI 910F
module or controller, only disconnect the 9-pole connector. Disconnecting the
25-pole connector will interrupt the CAN Bus.
M&I – AC 900F Controller
Connection of Freelance I/O racks
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