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. The port capacity of the Model
290 is 16, however, it may be expanded by coupling two or more Model
290's together via an RS-422 port. 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 4-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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