Contemporary Control Systems PC10420 Adapters - Manual (Page 7)

TD874100-0IH
7
-CXS Coaxial Star
In a coaxial star system, NIMs and hubs are interconnected in a point-to-
point fashion using coaxial cable. A NIM can connect to one other NIM or
can connect to an unused port on a hub. Hub-to-hub connections are
allowed.
In a two-node system, simply connect the two -CXS NIMs together using
RG-62/u coaxial cable. The length of cable cannot exceed 2000 feet.
If more than two NIMs are used on a network, either an active or passive
hub is required. With passive hubs, a maximum of four NIMs can be
interconnected. Unused ports on the passive hub must be terminated with a
93-ohm (nominal) resistor. The maximum length between a passive hub port
and a NIM is 100 feet.
Active hubs provide overall better performance than passive hubs since
greater distances can be achieved along with a degree of isolation. Connect
each NIM to a port on the hub using RG-62/u coaxial cable. This length of
cable cannot exceed 2000 feet nor can the length of cable between two
cascaded hubs exceed 2000 feet. However, up to ten hubs can be cascaded
thereby providing an overall cable length of 22,000 feet. Unused ports on
active hubs need not be terminated.
Figure 2—Active hubs can be cascaded
for greater distances.
-CXB Coaxial Bus
For hubless systems, the -CXB transceiver can be used. NIMs are
interconnected with RG-62/u cables and BNC Tee connectors. Each -CXB
NIM represents a high impedance connection in both the powered and
unpowered states. Therefore, passive termination must be applied to both
ends of a bus segment. Use BNC style 93-ohm (nominal) resistors at each
end. The maximum segment length is 1000 feet and the maximum number
of NIMs that can be connected to a segment is eight.
To extend a bus segment beyond 1000 feet, an active hub is required. If the
hub port is of the -CXS type, connection can be made if a few simple rules
are followed. Only connect this bus segment at the end of a segment. Do not
connect the hub to the middle of a segment since the hub port is not of the