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  • Synchronous or asynchronous
  • Single mode and multimode supported
  • Data rates up to 128 kbps sync and 115.2 kbps async
  • V.54 diagnostics, including local and remote loopbacks
  • Built-in BERT in compliance with V.52
  • Full or half duplex
  • Controlled or continuous carrier
  • Internal, external or receive clock
  • Transmission range up to 16 km (10 miles) over single mode fiber
  • LED indicators
  • V.24, V.35, X.21 or RS-530 interface options
  • Operates with an external power supply (except FOM - 9/V.24/UP)


  • The FOM - 9, Sync/Async Fiber Optic Modem, is used for local data distribution, connecting full or half duplex, sync or async terminals to computers over single mode or multimode fiber optic cable. FOM - 9 operates at data rates of 32 to 128 kbps in sync mode or 9.6 to 115.2 kbps in async mode. FOM - 9 operates at distances up to 16 km (10 miles) depending on the type of fiber optic cable.
  • Five FOM - 9 models are available:
    • FOM - 9/V.24/UP, unpowered, V.24 interface
    • FOM - 9/V.24, V.24 interface
    • FOM - 9/V.35, V.35 interface
    • FOM - 9/X.21, X.21 interface
    • FOM - 9/530, RS-530 interface.

    Each model has a 25-pin D-type connector for the DTE interface. The V.35 interface is supplied with a 45 cm (17.7") cable, with a 25-pin female connector on one side and a 34-pin female connector on the other side. The X.21 interface is supplied with a 45 cm (17.7") cable with a 25-pin male connector on one side, and a 15-pin X.21 female connector on the other side.

  • Asynchronous transmission is provided by internal conversion from async to sync, in compliance with ITU V.22 bis standard. Different async formats are switch-selectable.
  • The modem's carrier can be set for either continuous operation or for switched operation. In switched operation, the carrier is controlled by the RTS signal and enables transfer of a control signal end-to-end.
  • In synchronous mode, transmit timing can be provided by one of three user-selectable sources:
    • Internal oscillator
    • External clock
    • Loopback clock derived from the receive signal.
  • FOM - 9 performs diagnostic loops in compliance with ITU V.54 standard. Two V.54 loops are available: analog loop (V.54 Loop 3) and remote digital loop (V.54 Loop 2). These loops are activated either by a DIP switch or by the DTE interface Circuit 141 (pin 18) and Circuit 140 (pin 21). (Loopbacks in FOM - 9/X.21 can only be activated via DIP switch.) A proprietary local digital loop is available and can be activated only by the product's switches. This loop connects the local RD to the TD. A TST LED lights when any of the diagnostic loops is ON.
  • FOM - 9 includes a built-in V.52 standard BER tester for testing link integrity, activated by a DIP switch. The BER tester checks the receive data and turns on an ERROR LED, when an error is detected.
  • FOM - 9 incorporates all the advantages of a fiber optic system:
    • Lower attenuation than with copper wires; attenuation is not related to frequency
    • EMI/RFI immunity: saves the cost of expensive and heavy shielding and complex error checking routines
    • High data security: risk of eavesdropping is minimized as fibers radiate negligible power; cost of data encryption is reduced
    • Safety and electrical isolation: no spark hazard and no ground-loop noise problems.
  • FOM - 9 includes six LEDs for indicating signal status: RTS, TD, RD, CD, TST and ERR.
  • FOM - 9/V.24/UP's innovative circuitry design allows operation without power supply, by using ultra-low power from the standard RS-232/V.24 data and control signals. For proper operation, both data and control signals must be connected, i.e. TD, RD, RTS and DTR.

    If the DTE cannot provide enough power for normal operation of the unit, use FOM - 9/V.24.

  • FOM - 9/V.35, FOM - 9/X.21, FOM - 9/V.24 and FOM - 9/530 include a power jack for connection of an external power supply. An additional external 9V DC 500 mA adapter should be ordered separately and used to power the unit.