TD960801-0MC
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2.6.3
Extending the Backbone
The backbone side of the EXTEND-A-BUS must comply with
standard ARCNET cabling rules. Companion AI ARCNET
active hubs are available for extending the backbone cabling up
to 6 km using coaxial cabling and ten active hubs. When using
a fiber optic backbone, a maximum of 4.8 km can be achieved
requiring two active hubs. Hubs can be cascaded to reach the
required distance.
By using active hubs, star and distributed star topologies are
possible. There is, however, a limit to the overall length of the
backbone network. The delay experienced when an EXTEND-
A-BUS communicates to another EXTEND-A-BUS with each
located at the extreme ends of a network cannot exceed 31
µ
s.
This delay is due to cable and hub delays. This delay translates
to a maximum of 6 km of coaxial cable or 4.8 km of fiber optic
cable. When making this calculation, only consider the distance
between the two furthest EXTEND-A-BUSes. Also verify the
distance limitations of active hubs being used. Active hubs that
incorporate coaxial star ports (-CXS) allow for 2000 foot
connections between compatible ports but no bussing. When
making a connection to a -CXS port from the EXTEND-A-
BUS’ -CXB port, make sure that the -CXS port is located at
one end of the segment and that no terminator is used. The
length of a segment connecting a -CXB port cannot exceed
1000 feet (305 m).
