You can splice the orange wire to the head light switch.
When you turn your headlights on the scanner will automatically dim
... Should have read page 35.... , it's on page 36 of the BCD996T user guide :
Exactly how it is done on mine and suggested at the same page of the user guide (point #5). On my car (and others), the car radio and accessories stay on even after removing the key from ignition switch for 15 minutes or until I open a door within that time limit.Normally you would put the red to the accesory output of your ignition switch, not the battery (constant) to avoid leaving it on and running your battery dead.