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 baud. 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.

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. Alternatively, a convenient four-wire modular phone jack (RJ-11) is available.
  • DC to 57,600 Baud
  • Optical Isolation
  • Surge Protectors
  • LED Diagnostic Indicators
  • Operation to 3 Miles (5km) at 9600 Baud, 1 Mile (1.7km) at 19,200, 0.5 Miles (0.8km) at 57,600
  • Four-Wire Full Duplex, Two-Wire Simplex
  • Self-Powered or Host-Powered
  • Selection of Connectors
  • Wide Operating Temperature Range, 0 to +70°C
  • CE Compliant
General Purpose RS-232 Line Driver

LDM30 Devices


Part Number Configuration
Male, Host-powered, Screw termination
Male, European transformer, Screw termination
Male, U.S. transformer, Screw termination
Female, Host-powered, Screw termination
Female, European transformer, Screw termination
Female, U.S. transformer, Screw termination

Frequently Asked Questions


Can Dataforth provide calibration reports for modules I purchased?
Yes we can provide calibration reports for the modules that you purchased.

You can either
a) visit https://www.dataforth.com/TestDataReport.aspx to search for Test Report Datasheets by Serial Number or
b) you can send us a list of model numbers and their serial numbers to support@dataforth.com

Is the LDM35 a suitable replacement for the LDM30?
Please observe the block diagram in the datasheets of the LDM35 and LDM30 modules.

In the block diagram, you can see the direction of space current and mark current through terminals 3 and 4 (TD+ and TD-). Since these currents flow in the opposite direction between the LDM30 and LDM35, the LDM35 cannot be used to replace the LDM30.

We recommend replacing the LDM30 with another LDM30, or you can use the LDM70 as a suitable replacement as well.