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Full Isolated RS-232/485 Converters

LDM485 image

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 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 con-verter. 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 57.6 kbits per second. 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. 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 12 VAC from a wall-mounted transformer to screw terminals 1 and 2 on the RS-485 connector. Alternately, they can use ±12 VDC to pins 9 (+) and 10 (–) of the RS-232 connector.

Circuit diagram Dataforth LDM485

Block Diagram LDM485

PDF Downloads:

  • Produkt Overview LDM
  • Product Overview LDM

  • 2 Modules for Type LDM485:

    LDM485-P RS-232 Interface, Connector LDM485 Fully Isolated RS-232/485 Converter
    LDM485-S RS-232 Interface, Connector LDM485 Fully Isolated RS-232/485 Converter


    • Baud rates up to 57.600 Baud
    • Max. Distance 12.9 km at 2400 Baud
    • Asynchronous 4-Draht Full- / 2-Draht Half-Duplex, 2-Draht Simplex
    • Isolation 1000 Vrms
    • Isolation with Optcoupler and DC-DC Converter
    • Input Protection
    • LED`s for Installation, Startup and error diagnostics
    • RTS, ,CTS, DTR, DTS and RLSD-Controll-Lines
    • TD, RD, RTS and CTS Channel-lines
    • Tri-state Output, up to 64 units
    • Choice of different connectors
    • Power Supply AC: 12V, DC: (±) 11.5 VDC bis (±)17.0 VDC
    • Operating Temperature Range 0°C … +70°C
    • Dimensions 167.6 x 53.3 x 32.5 mm
    • CE Compliant
    • Special Solutions on request