Appendix E: Field Connections - Contemporary Controls Metasys JC-MER-CXB User Manual

Appendix E: Field Connections

The JC-MER-CXB transceiver presents a high-impedance connection
in both the powered and unpowered states. Although nominally a bus
device, it can be used in either bus or star ARCNET topologies that
use RG-62/u coaxial cable.
Regardless of the topology implemented, the coaxial port will require
a BNC Tee connector with at least one leg of the connector fastened
to coaxial cable. If the unit passes traffic from one portion of an
ARCNET bus to another, the remaining leg of the Tee connector will
tie to another coaxial cable. But if the unit occupies the end of a bus
segment, the remaining leg of the Tee connector must be fitted
with a BNC-style terminator having 93 (nominal) ohms of resistance.
The maximum ARCNET segment length is 1000 feet and the
maximum number of nodes per segment is eight. To extend a bus
segment beyond 1000 feet, an active hub is required. The coaxial
cable should attach directly to the hub port without using a BNC Tee
connector since the port internally terminates the end of a bus segment.
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