Serial interfaces cables and converters scheme
Used to verify the port is functional.

CheckIt/Norton/Passmark Loopback 

Name Pin Pin
Jumpering 1 2 3
Jumpering 2 4 5
Jumpering 3 6 8,20
Jumpering 4 15 17,24

Loopback, or loop-back, refers to the routing of electronic signals, digital data streams, or flows of items back to their source without intentional processing or modification. This is primarily a means of testing the transmission or transportation infrastructure. A communications transceiver can use loopback for testing its functionality. For example, a device transmit pin connected to its receive pin will result in the device receiving exactly what it transmits. Moving this looping connection to the remote end of a cable adds the cable to this test.

25 pin D-SUB female connector layout
25 pin D-SUB female connector
at the computer
25 pin D-SUB male connector layout
25 pin D-SUB male connector
at the loopback
According to 3 reports in our database (3 positive and 0 negative) this pinout should be correct.

Is this pinout
Serial port Loopback (25 pin) visual pinout:
Serial port Loopback (25 pin) diagram
click to enlarge
This page contain parts under Copyright © 2000-2018 by team.
No portion of this webpage may be reproduced in any form without providing visible HTML link to . Webmaster permission required in any other cases.
Efforts have been made to ensure this page is correct, but it is the responsibility of the user to verify the data is correct for their application.