Product FAQs

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How can I make sure my RS-422 serial port is working in Windows?


To check whether or not a RS-422 serial port is working, perform a RS-422 loopback test.

  1. Convert your serial port to be female if it is not already.  You can do this by taking a female/female cable or gender changer and plugging it into the serial port. 
  2. Take a metal paperclip or wire and cross pins T- with R- and T+ with R+.  The device or the manual should indicate what pins are T+, T-, R+ and R-.
  3. Open a telnet session on the COM port number in question.  To find out the COM port number of the device you want to test, please see “How do I check to ensure the COM port is listed properly in Windows XP, Vista, 7 or 8?”
  4. To open a telnet session on the COM port, you need a telnet client like PuTTY or Hyper Terminal. 
  5. Note: Windows XP comes with Hyper Terminal.

When the session is open, anything you type into it you should see.  The loopback test fails when you cannot see what you are typing in this window.

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