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Full Isolated RS-232 Line Drivers

LDM70 image

The LDM70 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 LDM70 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 bits per second. A handshake operation is implemented over the same two-wire pairs. A self-powered model and a host-powered model are available. The self-powered unit uses 12VAC 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. In addition, LEDs indicate valid carrier detect and data terminal ready.

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 LDM70

Block Diagram LDM70

PDF Downloads:

  • Produkt Overview LDM
  • Product Overview LDM

  • 2 Modules for Type LDM70:

    LDM70-P RS-232 Interface, Connector LDM70 Fully Isolated RS-232 Line Driver
    LDM70-S RS-232 Interface, Connector LDM70 Fully Isolated RS-232 Line Driver


    • Baud rates up to 57.600 Baud
    • Max. Distance 19.3 km at 1200 Baud
    • Asynchronous 4-Draht Full-Duplex, 2-Draht Simplex
    • Isolation 1000 Vrms
    • Isolation with Optcoupler and DC-DC Converter
    • Input Protection
    • LED`s for Installation, Startup and error diagnostics
    • DTR and RLSD-Controll-Lines
    • TD and RD Channel-lines
    • Choice of different connectors
    • Power Supply AC: 12 VAC, DC: ± 9 V to ± 15 V
    • Operating Temperature Range 0°C … +70°C
    • Dimensions 144.8 x 53.3 x 25.4 mm
    • CE Compliant
    • Special Solutions on request