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General Purpose RS-232 Line Drivers

LDM30 image

The LDM30 series of products is designed to allow video display terminals (VDTs) and other RS-232 devices to be connected over distances sufficient to cover any industrial or institutional complex of buildings. These line drivers feature a rugged aluminum enclosure small enough to mount on the back panel of VDT units, saving valuable desk and floor space.

The LDM30 series is designed for full-duplex, asynchronous operation over two, DC-continuity, non-loaded, twisted-wire pairs. Through special high-speed optically-coupled circuits they may communicate at data rates up to 57,600 bps. A self-powered model and a host-powered model are available. The self-powered unit uses 12 VAC from a wall-mounted transformer while the host-powered unit takes ±DC power from pins 9 and 10 of the RS-232 connector. The line driver circuits — and, consequently, the host device — are protected from electrical transients due to lightning strikes or operation of heavy industrial equipment.

Each device features a convenient Data-Communication Equipment (DCE) to Data-Terminal Equipment (DTE) switch which reverses pins 2 and 3 of the RS-232 connector. For installation and troubleshooting, each unit has diagnostic Light-Emitting Diodes (LEDs) on the transmit and receive lines.

The RS-232 connector may be ordered as a male or female 25-pin connector. Field connection is made through a modern, solderless, screw-termination assembly.

Circuit diagram Dataforth LDM30

Block Diagram LDM30

PDF Downloads:

  • Produkt Overview LDM
  • Product Overview LDM

  • 2 Modules for Type LDM30:

    LDM30-P RS-232 Interface, Connector LDM30 General Purpose RS-232 Line Driver
    LDM30-S RS-232 Interface, Connector LDM30 General Purpose RS-232 Line Driver


    • Baud rates up to 57.600 Baud
    • Max. Distance 19.3 km at 1200 Baud
    • Asynchronous 4-wire Full-Duplex, 2-wire Simplex
    • Isolation 300 Vrms
    • Optical Isolation
    • Input Protection
    • LED`s for Installation, Startup and error diagnostics
    • RTS, ,CTS, DTR, DTS and RLSD-Controll-Lines
    • TD and RD Channel-lines
    • Choice of different connectors
    • Power Supply AC: 12 VAC, DC: ± 9 V to ± 15 V
    • Via Host-PC
    • Operating Temperature Range 0°C … +70°C
    • Dimensions 91.4 x 53.3 x 25.4 mm
    • CE Compliant
    • Special Solutions on request