The LDM35 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 enclosure small enough to mount on the back panel of VDT units, saving valuable desk and floor space.

The LDM35 series does not require a power supply for operation. The use of low power circuits and a sensitive optical receiver allows the devices to derive all necessary power from the RS-232 data and control signal. They are designed for full-duplex, asynchronous operation over two, DC-continuity, non-loaded, twisted-wire pairs. Two-wire simplex operation may be accomplished over two wires. 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.
  • Signal-powered: No Power Source Required
  • Optical Isolation: Breaks Ground Loops
  • Heavy Duty Surge Protectors: Prevents Lightning Damage
  • LED Diagnostic Indicators: Simplifies Installation and System Troubleshooting
  • Operation to Two Miles (3.3km) at 9600 Baud, One-Half Mile (0.8km) at 19,200 Baud, Seven Miles (11.7km) at 1200 Baud
  • Four-Wire Full Duplex, Two-Wire Simplex
  • Selection of Connectors
  • Wide Operating Temperature Range, 0°C to +70°C
  • Null Modem Switch
  • CE Compliant
Signal Powered RS-232 Line Driver

LDM35 Devices


Part Number Configuration
Male 25-Pin Connector, Screw terminals
Female 25-Pin Connector, Screw terminals

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.