Omega Engineering DIN-190 - Manual (Page 4)

3 DIN-191 & DIN-192 USERS MANUAL
GENERAL DESCRIPTION
The DIN-191 and DIN-192 series converter boxes convert RS-232
communications signal levels to the correct electrical signals required by
RS-485. The RS-485 communications standard is recommended when
many modules, or other addressable devices, must be connected to a
host computer over long distances. The DIN-191 and DIN-192 converters
allow communications bus lengths up to 4,000 meters and baud rates up
to 115K baud using one twisted pair of wires.
The RS-485 communications standard is half-duplex; therefore data can
be transmitted in only one direction at a time. To determine the direction
of data on the RS-485 bus, many products require external handshaking
signals to control the bus direction when transmitting or receiving data.
This technique often requires that host RS-232 software be written, or
modified, to accurately control handshaking signals for proper system
operation. The DIN-191 and DIN-192 automatically control the bus
direction without external handshaking signals from the host. Therefore,
host software written for RS-232 may be used without modification. RS-
485 bus control is completely transparent to the user.
The DIN-192 is an RS-485 repeater. Repeaters are required to extend
communications bus lengths or allow more than 32 RS-485 devices to be
connected to a communications bus. A repeater simply re-amplifies, or
boosts, existing RS-485 signals transmitted over long distances.
The DIN-191 and DIN-192 are each isolated between the RS-232 port
and/or RS-485 ports and require a regulated +5Vdc power supply.