The LDM422 is a compact RS-232
to RS-422 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 on
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 RS422 connections are made
through convenient solderless
screw terminals.
The LDM422 series is designed for
full duplex operation over two-wire pairs. Outputs are tri-state, allowing
multidropping of up to 32 units.
Hardwarehandshake is available
over two separate wire pairs. Data
rates are 75 to 19,200 baud.
Six diagnostic LED indicators are
provided 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. The
RS-422 interface supports Request
To Send and Clear To Send on
separate wire pairs. The LDM422
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 or
±12VDC to pins 9 (+) and 10 (–) of
the RS-232 connector. The LDM422
conforms to EIA RS-232 and
RS-422 specifications. Data
Terminal Ready must be asserted
by the host RS-232 port before the
LDM422 can transmit data. When
Data Terminal Ready is not
asserted all outputs of the LDM422
are high impedance, allowing up to
32 LDM422 units to be multidropped
on a common communications cable.
See Figure on page 2 for details.
Request To Send and Clear To
Send are carried through the
RS-422 port as two separate wire
pairs. These may be used for full
duplex flow control.
† All dollar amounts on this site are shown in Singapore currency.
Note: Includes operator’s manual. Transformer powered units also include 120 Vac wall mount transformer.
