Danfoss FCM 300 Operating Instructions Manual page 13

The bus termination - FCM 300
1 = RxD/TxD-P∼ (red cable)
It is essential that the bus line is terminated properly.
A mismatch of impedance may result in reflections
on the line that will corrupt data transmission.
- The PROFIBUS is provided with a suitable
termination which may be activated by the switches
of the RS485 switch block located just to the left of
the terminal block X100 (see drawing below). The
switches should be on to terminate the bus.
NB!:
The switches should never be left in opposite
positions. They should either both be
ON or both be OFF!
- Most masters and repeaters are equipped
with their own termination.
- If an external termination circuit consisting of three
resistors is connected to the bus line a 5 V d.c.
power supply must be used, please note that this
must be galvanically isolated from the a.c. line.
12
FCM 300 / FCD 300 / VLT
®
2800 / DP V1 PROFIBUS
2 = RxD/TxD-N∼ (green cable)
MG.90.A5.02 - VLT is a registered Danfoss trademark