Contemporary Control Systems EXP Expansion Modules User Manual - Manual (Page 15)

Fiber optic connections require a duplex cable arrangement.
Two unidirectional cable paths provide the duplex link.
There
are two devices at each port on the MOD HUB expansion
module.
One device, colored light gray, is the transmitter and
the other, dark gray, is the receiver.
Remember that “light goes
out of the light (gray).”
To establish a working link between a
hub and a network interface module or a hub to another hub, the
transmitter of point A must be connected to a receiver at point
B.
Correspondingly the receiver at point A must be connected to
a transmitter at point B.
This establishes the duplex link which
is actually two simplex links.
Fiber optic cable is available
paired for this purpose.
Usually the manufacturers’ labeling is only on one cable of the
pair which is handy for identifying which of the two cables is
which.
Establish your own protocol for connecting cable
between hubs and NIMs in the field using the manufacturers’
labeling as a guide.
But remember that to connect point A to
point B requires a paired fiber optic cable and that the light
gray connector at one point must connect to a dark gray
connector at the other point.
2.5.6 Connecting DC-Coupled EIA-485 Networks
One RJ-11 connector is provided for each DC-coupled EIA-485
segment. This segment can be up to 900 feet long of IBM Type
3 unshielded twisted-pair cable, and as many as 17 nodes can
occupy the segment.
Make sure that the phase integrity of the
wiring remains in tact.
Pin 3 of the modular jack on each NIM
and hub port must be connected together.
The same applies to
pin 4.
Most modular (satin cable) telephone wiring flips the
phase of the wiring thereby reversing the connections to pins 3
and 4 at each end.
Do not use this type of cable. Some modular
cable is not even twisted. Be sure to use the proper cable.
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