This command only works on laptop/netbook computers.
It allows you to change the brightness of the laptop screen.
The [level] parameter is brightness value to change.
positive value increases the brightness, and negative value decreases the brightness.
{mode} is optional parameter that
may conatin the following values:
1 = Change the brightness under AC power.
2 = Change the brightness under DC power.
3 = Change the brightness for both AC power amd DC power (The default).
Examples:
changebrightness 7
changebrightness -10
changebrightness 5 2
