W&T connects
Interfaces for TCP/IP, Ethernet, RS-232, RS-485, USB, 20mA, glass and plastic fiber optic cable, http, SNMP, OPC, Modbus TCP, I/O digital, I/O analog, ISA, PCI
Data sheet:

Universal FO-Interface 20mA

  • Universal FO Interface 20mA

Reliably transmit TTY over very long distances

The model 41215 Interface features a selectable active or passive 20mA interface which the converter changes into a universal optical interface for single-mode and multi-mode glass fiber optics.



  • 1x 20mA
    • 9-pin Sub-D plug
    • Selectable active or passive mode
    • Alternate designations: Current loop, TTY, line current interface
  • 1 x single-mode / multi-mode glass fiber optics
    • SC connector

Management and connectivity:

  • No re-configuration of transmission parameters required
  • Universal 20mA interface for singlemode and multimode glass fiber optics
  • Active/Passive mode can be set individually for both loops
  • Noise-immune transmission over a distance of up to 20 km
  • Galvanic isolation up to nearly any value between the connected devices

Voltage supply:

  • External
    • 12V-48V DC via plug-in screw terminal
    • Galvanically isolated power connection

Standards & more

  • Conforms to standards both in office and industrial environments:
    • High noise resistance per EN 61000-6-2
    • Low noise emission per EN 55032:2015 + A1 Cl. B, EN 61000-3-2 & EN 61000-3-3
  • 5 year guarantee

Worth knowing

Data transmission over long distances and in extremely noisy environments make the use of fiber optics the logical choice as a physical transmission medium.

The use of plastic fiber optics allows easy-to-install connections over relative short distances of up to 100 meters. But for distances above this limit the use of glass fiber optic cable is unavoidable.

While distances of up to 4km are easily accomplished with multimode fiber optics, greater distances are the domain of singlemode fiber optics.

It used to be that routing and assembling glass fiber optics created significant problems for the users, but today - thanks to the wider use of glass fiber technology in networking - many companies are offering this work as a service.

Technical data

Connections and displays:

  • Serial port:
    • 20mA interface
    • 9-pin SUB-D adapter
  • Glass fiber optics port:
    • SC connector
  • Operating modes:
    • active or passive operation
  • Baud rate:
    • 0..19,200 baud
  • Data format:
    • any format
  • Supported signals:
    • RxD, TxD
  • Fiber-optic medium:
    • Singlemode fibers 9/125µm or
    • Multimode fibers 50/125µm or 62.5/125µm
  • Fiber end face:
    • UPC (Ultra Physical Contact)
  • Transmitter type:
    • Class 1 Laser Product
  • Wavelength:
    • 1310nm
  • Optical output power:
    • Singlemode fibers: min. -12dBm, max. -8dBm
    • Multimode fibers: max. -3dBm
  • Receiver sensitivity:
    • max. -22dBm
  • Maximum input power:
    • max. -3dBm
  • Optical budget:
    • min. 10dB
  • Maximum distance:
    • Singlemode fibers: min. 20km @0.35dB/km
    • Multimode fibers: min. 5km @1dB/km
  • Minimal attenuation:
    • Singlemode fibers: 0dB
    • Multimode fibers: 3dB
    • (below this value use of an
    • attenuation member may be required - e.g. W&T #81900)
  • Galvanic isolation:
    • Isolation voltage min. 1kV DC between supply and serial connection
  • Supply voltage:
    • 12..48V DC
  • Current consumption:
    • typ. 80mA @12V DC, 40mA @24V DC
  • Supply connection:
    • Plug-in screw terminal, 5.08mm spacing
    • Labeled "L+" and "M"
  • Displays:
    • 1x LED Data
    • 1x LED Power

Housing and other data:

  • Housing:
    • Plastic housing for top hat rail installation
    • 105 x 22 x 75mm (L x W x H)
  • Enclosure rating:
    • IP20
  • Weight:
    • approx. 120g
  • Ambient temperature:
    • Storage: -40..+70°C, Operation: 0..+60°C
  • Permissible relative humidity:
    • 5..95% RH (non-condensing)
  • MTBF:
    • 291,514h @25°C per MIL-HDBK-217
  • Life expectancy:
    • > 25 years at 25°C ambient temperature
  • Scope of delivery:
    • Universal FO-Interface 20mA
    • Please order power supplies separately as accessories


*Net unit price for
commercial users
  • Power supplies

    • Plug-in power supply, 24V / 500mA DC with Euro plug
    • 11021
    • 21.00€
    • Plug-in Power Supply, 24V / 750mA DC with Euro, US and UK plug
    • 11026
    • 38.00€
    • Power supply for DIN rail, 24V / 630mA DC
      (merchandise, 2-year manufacturer’s guarantee)
    • 11080
    • 33.00€
  • Mechanical Accessories

    • Mounting bracket for wall mounting
    • 58812
    • 11.20€
    • 19" DIN rail
    • 58813
    • 21.00€

* Our offering is intended only for commercial users. We will be happy to refer private end customers to trading partners through whom our products can be purchased.