Serial Port Loop Back, DB 25 Pin Female, XT Type Adapter Shorts
 Pin connection: 2-3, 4-5, 6-8-20-22. |  | Serial Port Loop Back, DB 9 pin Male, AT Type Adapter Shorts
 Pin connection: 1-4-6-9, 2-3, 7-8. |  | Serial Port Loop Back, DB 9 pin Female, AT type
 Pin connection: 1-4-6-9, 2-3, 7-8. |