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3.2 Terminal Arrangement and Signal Names and the Connection Procedure of the RS-422A/485 Communication Interface
3-6
For a two-wire system, the host computer must control the transmission driver of the
converter in order to prevent collisions of transmit and received data. When using the
recommended converter, the driver is controlled using the RS (RTS) signal on the RS-
232.
• When Instruments That Support Only the RS-422A Interface Exist in the System
When using the four-wire system, up to 32 recorders can be connected to a single
host computer. However, this may not be true if instruments that support only the RS-
422A interface exist in the system.
When the instrument that support only the RS-422A interface exist in the
system
The maximum number of connection is 16. Some of OMEGA's conventional recorder
only support the RS-422A driver. In this case, only up to 16 units can be connected.
Note
In the RS-422A standard, 10 is the maximum number of connections that are allowed on one
port (for a four-wire system).
• Terminator
When using a multidrop connection (including a point-to-point connection), connect a
terminator only to the recorder on the end of the chain. In addition, turn the terminator
on the host computer ON (see the computer's manual). If a converter is being used,
turn ON its terminator. The terminator must be attached externally to the
recommended converters.
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