The USB ports on the Cisco VXC 2112/2212 operate at two power levels:
Low: 0.5 watts
High: 2.5 watts
USB ports that operate at the low-power level can only power USB devices that consume up to 0.5 watts of power, and USB ports that operate at the high-power level can power USB devices that consume up to 2.5 watts of power.
USB ports on the Cisco VXC 2112/2212 that operate at high power cannot individually power any noncompliant USB accessory that requires more than 2.5 watts of power. To power devices that require between 2.5 and 5 watts of power, you can use a USB Y cable to connect the accessory to USB port 3 and 4 of the client (when these are operating at high power).
In addition, if no device is connected to a port, the Cisco VXC 2112/2212 cannot reallocate the available power from this port to a device on another port. For example, if USB ports 1 and 2 are operating at low power and no device is connected to port 2, the Cisco VXC 2112/2212 cannot redirect the power allocated to port 2 to power a high-power device on port 1. In this case, the maximum power limit on port 1 remains unchanged at 0.5 watts.
Low-power USB devices (0.5 watts or less) are typically keyboards, mice, and joysticks, while high-power USB devices (greater than 0.5 watts) are typically bus-powered cameras, hubs, and some USB Flash drives.