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:

RS422/RS485-Isolator Industry with overvoltage protection

  • RS422/RS485 Isolator Industry with OVP

Serial Isolator with overvoltage protection

The model 66203 Isolator with integrated overvoltage protection enables galvanically isolated connection between RS422 devices and RS485 bus systems.



  • 2x RS422/RS485
    • 9-pin Sub-D connector
  • Galvanic isolation between the ports
    • Isolation voltage 1kV DC

Management and Connectivity:

  • Automatic control in RS485 operation
  • No re-configuration of transmission parameters required
  • High transmission speeds of up to 3 Mbaud

Power supply:

  • External
    • 12V-24V AC/DC via plug-in screw terminal
    • Galvanically isolated power connection
  • Integrated overvoltage protection

Standards & more

  • Conforms to standards both in office and industrial environments:
    • High noise resistance for industrial environments
    • Low noise emission for residential and business areas
  • 5 year guarantee

Worth knowing

Overvoltage protection for RS485 ports:
The maximum permissible differential voltage that can affect RS485 transceiver components from the outside is generally limited to values of around ± 12..14V. Voltages that exceed these values will always result in destruction of the interface components.

When using shielded cable, it is unlikely that such high differential voltages will occur, since extreme coupling onto the transmission line expresses itself as a rise in potential on all cable conductors.

When using the isolator on transmission lines outside of buildings or when the cabling conditions are unclear, use of the 66203 Isolator is recommended. This isolator model has built-in overvoltage protection, which limits the maximum occurring differential voltages to a harmless ±9V using fast protection diodes.

Technical data

Connections and displays:

  • Serial ports:
    • RS422/RS485 interfaces, selectable
    • 9-pin SUB-D adapter
  • Operating modes:
    • RS422
    • RS485 4-wire with automatic control
    • RS485 2-wire with automatic control
  • Switching time:
    • Settable 10µs / 50µs for switching from data sending to receiving
    • for RS485 automatic control (can be changed on request)
  • Termination:
    • Connectable termination network for RS485 operation
  • Overvoltage protection:
    • Differential voltage limited by Transil diodes
  • Baud rate:
    • 0..3 Mbaud
  • Data format:
    • any format
  • Galvanic isolation:
    • min. 1kV DC between all terminals
  • Supported signals:
    • RxD, TxD, CTS, DTR
  • Supply voltage:
    • 12..24V AC/DC (±10%)
  • Current consumption:
    • typ. 70mA @12V DC, 35mA @24V DC
  • Supply connection:
    • Plug-in screw terminal, 5.08mm spacing
    • Labeled "L+" and "M"
  • Displays:
    • 1 LED Power
    • 1 LED Data

Housing and other data:

  • Housing:
    • Plastic housing for top hat rail installation
    • 105 x 22 x 75mm (L x W x H)
  • Weight:
    • approx. 100g
  • Ambient temperature:
    • Storage: -40..+70°C
    • Operating in non-rowed installation: 0..+60°C
    • Operating in rowed installation 0..+50°C
  • Permissible relative humidity:
    • 5..95% RH (non-condensing)
  • MTBF:
    • 482,916h @25°C per MIL-HDBK-217
  • Life expectancy:
    • > 25 years at 25°C ambient temperature
  • Scope of delivery:
    • RS422/RS485 isolator, Industry
    • Please order power supplies separately as accessories


  • 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€
  • Cable and Connector Accessories

    • DB9F connection cable with open cable ends, left angled, 1.5m
    • 11902
    • 17.50€
    • DB9F connection cable with open cable ends, right angled, 1.5m
    • 11903
    • 17.50€
    • 9-pol. SUB D socket with screwing terminal and shielded housing
    • 11905
    • 21.00€
  • Mechanical Accessories

    • Wall mount housing, enclosure rating IP66 / IP67
    • 11120
    • 54.00€
    • 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.