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Fiber Optic Converters

LDM85 image

The LDM85 is a small, inexpensive fiber optic transmitter/receiver. It features a complete RS-232/422/423 port as well as high speed TTL data transmit and receive. It is capable of data rates from DC to 5 Mbps. A pair of these units allows most RS-232C cable links to be replaced and extended with a duplex fiber optic cable. The normal 50-foot RS-232 limit may be extended to 1.2 miles (2 km). Fiber optic data communications provide complete EMI/RFI rejection, isolation, elimination of ground loops, and reduced error rates. Data security is enhanced by almost nonexistent electromagnetic emissions. A unique multipoint capability allows local area networks to be formed with the isolation and data security of a fiber optic data highway.

The LDM85 is packaged in a rugged aluminum enclosure small enough to mount on the back panel of typical computer equipment, saving valuable desk and floor space. The RS-232 connection is through male or female EIA 25-pin connectors. The fiber optic connection is either through SMA (905) or ST connectors. Additional features include a TD/RD reversing switch for connection to DTE (Data Terminal Equipment) or DCE (Data Communication Equipment) ports, three diagnostic LED indicators, and locally connected handshake lines. The TTL port combined with the RS-232 port may be interfaced to RS-422/423 ports in 4-wire point-to-point mode only.

Circuit diagram Dataforth LDM85

Block Diagram LDM85

PDF Downloads:

  • Produkt Overview LDM
  • Product Overview LDM

  • 2 Modules for Type LDM85:

    LDM85-P RS-232 Interface, Connector LDM85 Fiber Optic Converter
    LDM85-S RS-232 Interface, Connector LDM85 Fiber Optic Converter


    • Baud rates up to 5 MBaud
    • Max. Distance 2 km at 5 MBaud
    • Asynchronous 2-Fiber Full-Duplex, 1-Fiber Simplex
    • Isolation through Fiber-Optic cable
    • DCE/DTE Switch
    • SMA- or ST- compatible
    • LED`s for Installation, Startup and error diagnostics
    • RTS, ,CTS, DTR, DTS and RLSD-Controll-Lines
    • TD, RD, TTL TD and TTL RD channel-lines
    • Power Supply AC 120/220VAC or 10-20VAC or DC +8 - +24VDC or +5VDC
    • Operating temperature range -40°C … +85°C
    • Dimensions 95.3 x 53.3 x 25.4 mm
    • CE Compliant
    • Special Solutions on request