The USB port uses a USB Type A connector, which has four pins. Two of the pins are used for power and two for data. Figure 3-1 is an illustration of a Type A USB port. Table 3-1 shows the pin assignments.
Figure 3-1 USB Type A connector
![[image: ../art/dsl02.gif]](../art/dsl02.gif)
| Pin | Signal name | Description |
| 1 | VCC | +5 VDC |
| 2 | D– | Data – |
| 3 | D+ | Data + |
| 4 | GND | Ground |
The iBook provides power for the USB ports at 5 V and up to 500 mA each.
Each USB port supports both low-speed and high-speed data transfers, at up to 1.5 Mbps and 12 Mbps, respectively. High-speed operation requires the use of shielded cables.
The Macintosh USB system software that comes with the iBook computer supports all four data transfer types defined in the USB specification.