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Product Description
The Model 290
RS-232 to RS-422/RS-485
Concentrator offers a unique group
of features for those applications using RS-422 and/or RS-485 for
communications between a multiplicity of devices. Based upon a
master-slave relationship. The Model 290 lets users expand RS-485
networks to 496 nodes, breaking the restriction of RS-485 that limits a
network to 32 nodes. Greater network capacity is possible by cascading
Model 290's. Industrial control applications are a prime example of the
use of this type of communications protocol. The 16 discrete ports on
the wiring hub provides the advantage of isolation between ports thus
increasing overall reliability of the network.
In a conventional RS-485
network a single node failure can crash an entire network, but now the
Model 290 isolates any node failure from affecting the network. The
master port of the Model 290 is configured for RS-232 and uses Transmit
Data, Receive Data and Ground. The Model 290 incorporates a built-in
interface converter to condition the signals between the master port and
any of the slave ports. These are operator programmable to RS-422 or
RS-485, simply by setting a dip switch for the respective port on the
rear panel. The port connectors are RJ-11 type. Internal intelligence
allows the Model 290 to support half duplex operation on the RS-485
single twisted wire pair without the requirement of RTS on the master
port. Full duplex operation is supported on the RS-422 ports over two
twisted pairs. Power for the Model 290 is supplied from a wall mounted
transformer with an eight foot connectorized line cord. Every port is
surge protected and the unit is equipped with a grounding stud to allow
a connection to earth ground for diversion of the otherwise deadly
effects of induced surges.
The 16 ports are available
on 6-wire, 6 position, RJ-11 connectors. Wiring is consistent with Telco
standards wherein the inner two contacts represent the transmit pair for
RS-422. The outer pair of contacts in the RJ-11 modular connector
represents the bi-directional pair for RS-485 or the receive pair for
RS-422.
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