The USB ports use USB Type A connectors, which have four pins each. Two of the pins are used for power and two for data. Figure 3-1 is an illustration of a Type A port and matching connector. Table 3-1 shows the pin assignments.
Figure 3-1 USB Type A port
![[image: ../art/iv03.gif]](../art/iv03.gif)
| Pin | Signal name | Description |
| 1 | VCC | +5 VDC |
| 2 | D– | Data – |
| 3 | D+ | Data + |
| 4 | GND | Ground |
The computer provides 5-volt power at 500 mA for each of the two ports.
The USB ports support both low-speed and high-speed data transfers, at up to 1.5 Mbits per second and 12 Mbits per second, respectively. High-speed operation requires the use of shielded cables.
The PowerBook G4 computer comes with version 1.3 of the Macintosh USB system software, which supports all four data transfer types defined in the USB specification.
USB devices can provide a remote wakeup function for the computer. The USB root hub in the computer is set to support remote wakeup whenever a device is attached to the bus.