Fully Isolated Limited Distance Modem, RS-232/485 Converter |
| LDM485 Series |
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Fully Isolated Limited Distance Modem, RS-232/485 Converter
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Complete Isolation
with Optical Couplers
and Power DC-to-DC
Converter
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Industrial Surge
Protection Devices
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Six LED Diagnostic
Indicators
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19.2K Baud at 3 Miles
(5KM), 57.6K Baud at
0.5 Miles (0.8KM)
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Request-to-Send, Clear-to-
Send Handshake
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Tri-State Outputs for
Multidrop Applications,
up to 64 Devices
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Selection of Connectors
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Wide Operating
Temperature Range
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Solderless Screw
Terminal Field
Connections
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View related products - Communication Products and Converters
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The LDM485 is a compact RS-232
to RS-485 converter which features
a complete electrical isolation
barrier and heavy duty electrical
surge protectors. These devices
feature a rugged aluminum
enclosure small enough to mount the back panel of typical computer
equipment, saving valuable desk
and floor space. Isolation is
provided by optical couplers and a
DC-to-DC converter. The RS-232
connection is through male or
female EIA 25-pin connectors. The
RS-485 connections are made
through convenient solderless
screw terminals.
The LDM485 series is designed for
full duplex operation over two-wire
pairs. Outputs are tri-state, allowing
multidropping of up to 64 units.
Hardware handshake is available
over two separate wire pairs. Data
rates are DC to 57.6k baud. Six
diagnostic LED indicators are
provided (see Figure 1) for
installation guidance and system
troubleshooting. The RS-232 interface supports Request To
Send, Clear To Send, Data Set
Ready, Received Line Signal
Detect, and Data Terminal Ready.
A convenient null modem switch is
provided for the data lines. Also, a
line termination switch connects a
line termination resistor and line
bias resistors to the RS-485 receive
lines. The RS-485 interface
supports Request To Send and
Clear To Send on separate wire
pairs. The LDM485 may be used to
convert two sets of send and
receive channels by using RTS and
CTS circuits as the second data
channels. Data rates are the same.
The units use 12VAC from a
wall-mounted transformer to screw
terminals 1 and 2 on the RS-485
connector. Alternately, they can use
±12VDC to pins 9 (+) and 10 (–) of
the RS-232 connector.
The LDM485 conforms to EIA
RS-232 and RS-485 specifications.
Data Terminal Ready must be
asserted by the host RS-232 port before the LDM485 can transmit
data. When Data Terminal Ready is
not asserted, all outputs of the
LDM485 are high impedance,
allowing up to 64 LDM485 units to
be multidropped on a common
communications cable. See Figures
1 and 3 for details.
Request To Send and Clear To
Send are carried through the
RS-485 port as two separate wire
pairs. These may be used for full
duplex flow control.
Data Terminal Ready, DTR, must
be asserted before the LDM485 can
transmit data. This is normally done
by the host computer. For situations
where the host equipment does not
have the capability of supplying a
DTR signal, RLSD may be used to
automatically assert DTR. On the
RS-232 connector P1 of each
LDM485, simply connect RLSD
pin 8 to DTR pin 20. This
connection is not appropriate for
multi-drop installations.
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† Price are shown in RMB.
Note: Includes operator’s manual. Transformer powered units also include 120 Vac wall mount transformer.
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Keywords:Fully Isolated Limited Distance Modem, RS-232/485 Converter
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