Contemporary Control Systems AI Active Hubs - Manual (Page 18)

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2.6.3 Connecting Twisted-Pair Bus Networks (-TPB)
Some AI2 link and repeater models have twisted-pair
transceivers (-TPB) which allows the insertion of an AI at any
point within a bus segment. Usually IBM type 3 unshielded
twisted-pair cable is (UTP) used, although shielded cable can
be used as well. A removable 5-position screw connector is
used to make connections. The middle pin is reserved for the
shield connection while phases A and B are available on each
of two pins to facilitate daisy-chain connections (within a bus
segment) or to attach a passive termination (at the end
devices). End devices require a passive terminator that matches
the impedance of the cable (typically 100 ohms).
2.6.4 Connecting Fiber Optic Cable (-FOG)
Multimode fiber optic cable is typically available in three sizes,
50/125, 62.5/125, and 100/140. The larger the size, the more
energy that can be launched and, therefore, the greater the
distance. Bayonet style ST connectors, similar in operation to
BNC coaxial cable connectors, are provided for making the
fiber connections.
Fiber optic connections require a duplex cable arrangement.
Two unidirectional cable paths provide the duplex link. There
are two devices on the AI fiber port. 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. However, remember that to connect point A