A dual-ended serial wrap plug used to test serial ports for operation. This particular wrap plug has both DB-25 and DB-9.
A very nice addition to any tech's tool kit.
These work great and can test additional wires besides just the send and recieve.
DSUB 9 pin FemaleDSUB 9 Female Connector
DSUB 25 pin FemaleDSUB 25 Female Connector
Wiring
Wired Together
DB-25 port: 2-3, 4-5, 6-8-20-22.
DB-9  port: 3-2, 7-8, 6-1-4-9.
Originally Used with IBM PC Diagnostic Software.
Used with Checkit Software.
For a fast test install and use Terminal it should echo back.