Lenovo ThinkPad traditional square tip connector is 7.9mm x 5.5mm with a central ID pin, used on ThinkPad T X and L series laptops from early 2000s until 2015 when the slim tip replaced it.
| Pin | Name | Function | Type |
|---|---|---|---|
| 1 | Center+ | DC positive 20V | PWR |
| 2 | Outer- | DC ground return | GND |
| 3 | ID | ThinkPad ID signal pin | BUS |
Lenovo ThinkPad traditional square tip connector is 7.9mm x 5.5mm with a central ID pin, used on ThinkPad T X and L series laptops from early 2000s until 2015 when the slim tip replaced it.