RS422 RS485 Isolator
Model: RPT-485_422-4 $119.95 In stock Order opto isolated rs232 to rs422 converters
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The RPT-485_422-4 is a multi-function, rugged, industrial-grade, RS422/RS485 isolator/repeater/converter, which can be used to isolate one group of RS-485/RS-422 equipment from another, or to extend the RS-485 or RS-422 distance to up to 4000 ft (1.2km); it can also can be used to convert a two-wire RS-485 signal into a four-wire RS-422 signal, and vice versa. This industrial RS422 RS485 isolator/repeater/converter operates within a temperature range of -40ºF to 185ºF (-40ºC to 85ºC), features 2500V opto-isolation, 600W surge protection and 15kV ESD static protection circuitry, which effectively protects your RS485/RS422 devices from ground loop, noise problems, transient surges, remote lightning and spikes. The unit supports data rates up to 115.2K Baud, and features data format auto-sensing and self-adjusting, which automatically adjust baud rate, parity, stop bit and other COM port parameters to the devices that it is connected to. Therefore, it requires no DIP switch / jumper settings, software drivers or flow control, making the unit a highly reliable and truly plug-and-play device. A separate external power supply is included in the package, and, thanks to the professional and unique casing design, the product can be mounted directly on a wall, panel or DIN Rail, without a need of using any unsecured DIN-Rail or wall-mount brackets.

CommFront's serial converters were strictly certified by SGS and/or TUV (both are the Nationally Recognized Testing Laboratories [NRTLs] in North America (approved by OSHA) and the Notified Bodies in the European Union. CommFront's product quality is ensured by our ISO 9001:2008 (Cert No. SG12/04213) quality control system (strictly certified by SGS/UKAS), and we back our high-quality converter products with a 30-day risk-free money-back guarantee and a 5-year replacement warranty.



Isolated RS422 RS485 Isolator
Opto-Isolated RS422 RS485 Isolator
RS485 Isolator
RS422 Isolator
RS485 Opto-Isolator
RS485 Isolated Converter


  • Isolate one group of RS-485/RS-422 equipment from another.
  • Converts 2-wire RS485 to 4-wire RS422 and vice versa.
  • Extends RS485 or RS422's distance.
  • 2500V optical isolation effectively protects RS-485/RS-422 devices from ground loops, noise problems, transient surges, remote lightning and spikes.
  • 300 to 115.2K Baud operation (auto-sensing & self-adjusting).
  • RS-485/RS-422 auto-detection, no software drivers or manual setting is required.
  • External 9-30VDC powered (included).
  • Industrial grade enclosed in a rugged, rustless ABS housing.
  • Plug and play (hot-pluggable, data format auto-sensing & self-adjusting).
  • Data direction auto-turnaround, no flow control is required.
  • Operating temperature: -40ºF to 185ºF (-40ºC to 85ºC).
  • Built-in 600W surge protection, 15kV static protection and circuit protection.
  • Direct DIN-Rail (Rack) or Wall / Panel mounting.
  • Surface Mount Technology manufactured to RoHS and ISO-9001 standards.
  • Safety: Strictly certified by TUV (Cert No. SG-CE-100004; SG-FCC-100001).
  • 5-year manufacturer's warranty.


Part Number: RPT-485_422-4
Compatibility: EIA/TIA RS-485 and RS-422 standards
Power Source: 9 to 30VDC (External AC to DC power adapter included)
External AC/DC Power Adapter: 9VDC/500mA (Input: 100~240VAC 50/60Hz, US type A plug)
Current Consumption: Less than 30mA
Optical Isolation: 2500Vrms (AC, 1 min)
Baud Rates: 300 to 115,200bps (auto-sensing and self-adjusting)
Distances: RS-485/RS-422: up to 4000ft (1.2km) at 19,200bps
Connectors: 2x 10-way Terminal Block
Surge protection: 600W
Static protection (ESD): Up to 15KV
Dimensions (H x W x D): 4.9 x 3.6 x 0.9 in (125 x 73 x 33 mm)
Weight: 4.5 oz (128 g) (with terminal block)
Operating Temperature: -40ºF to 185ºF (-40ºC to 85ºC)
Operating Humidity: Up to 90% RH (no condensation)


RS485/RS422 Side

Pin TX+/A+ TX-/B- GND2 RX+ RX- 9-30V GND1
RS485 485+ 485- RS485 GND2 - - DC+ DC/RS485 GND1
RS422 TX+ TX- RS422 GND2 RX+ RX- DC+ DC/RS422 GND1

RS422 RS485 Isolator Terminal Block

Terminal Block #1 (upper side)

RS422 RS485 Isolator Terminal Block 2

Terminal Block #2 (lower side)


No jumper setting is required for RS485/RS422 modes (auto-detection)


Isolated RS485 to RS422 converter
Figure 1: Two-wire RS-485 <=> Four-wire RS-422 Conversion

RS485 isolator connection
Figure 2: Two-wire RS-485 Isolator / Repeater
(Note: The maximum number of supported nodes depends on the RS-422 master)

RS422 isolator connection
Figure 3: Four-wire RS-422 Isolator / Repeater
(Note: The maximum number of supported nodes depends on the RS-422 master)


RS485 RS422 Isolator DIN rail mounting

Figure 4: DIN-Rail (Rack) Mounting

RS422 RS485 Isolator Wall mounting

 Figure 5: Wall/Panel Mounting



1) Make sure the power is connected and turned on.
2) Check the connections according to the above “CONNECTIONS” diagrams.
3) Loopback Test:

RS422 RS485 Isolator loopback test
  • Connect an RPT-485_422-4 to your PC's RS-485 or RS-422 port, and then connect TX+ to RX+ and TX- to RX- on the other side of the RPT-485_422-4.
  • Run 232Analyzer FREE version software on your computer.
  • Select "ASCII" for both the Send and Receive data formats. Then send command and/or string such as "CommFront" from the 232Analyzer software. You should receive an echo of the command/string sent ("CommFront"). By performing a simple loopback test like this, you can test both the transmitter and receiver of the isolator. This is very helpful when you are in doubt about the performance of your isolator.

RS422 RS485 Isolator - loopback test 2
Screenshot: Send/receive commands from 232Analyzer software.

232Analyzer is an advanced RS232 Serial Protocol Analyzer software that allows you to control, monitor and analyze serial port (RS232 / RS485 / RS422 / TTL, etc.) activities. Not just the data, it also allows you to monitor or change RS-232's line states: RTS, CTS, DTR, DSR, DCD, and RI.

The FREE version (no time limitation) can be downloaded from here.


RS-232: 3 easy steps to understand and control your RS232 devices
RS-485/RS422: Building a reliable RS485/RS422 network