RS232 DB25 Serial Loopback for CheckIt
The PC loopback plug is a useful diagnostic tool. The loopback plug connects serial inputs to serial outputs so that the port may be tested. There is more than one way to wire up a loopback plug - but this is the most common. Used to verify that a port is working. This one works with CheckIt.
 | DB25 pin D-SUB male (at the computer) |
| Name | Pin | Pin | Pin | Pin |
|---|---|---|---|---|
| Jumpering 1 | 2 | 3 | ||
| Jumpering 2 | 4 | 5 | ||
| Jumpering 3 | 6 | 8 | 20 | 22 |