RS232 DB9 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.
 | DB9 pin D-SUB male (at the computer) |
| Name | Pin | Pin | Name |
|---|---|---|---|
| CD | 1 | 6 | DSR |
| CD | 1 | 9 | RI |
| RXD | 2 | 3 | TXD |
| DTR | 4 | 6 | DSR |
| RTS | 7 | 8 | CTS |
DB9 loopback (variant #2)
DB25 loopback (variant #1)
DB25 loopback (variant #2)