When you plug in a live USB cable, the scanner is always on external power. The menu that pops up when you insert the cable allows you to choose between serial (normal scanning) and mass storage (programming) modes.
i use my verizon usb/wall adapter to power my scanner rather than the usb computer. same #s as the one sold on scannermaster and i luckily had an extra. but, the cord they sent is so damn short. u can use an extension cord of course. be nice if they included a longer cable. i rarely use the wall unit anyway as i have plenty of rechargeable batteries. if i go to a hotel and want to use it as a base in the room, then i may use the wall charger.
just had an idea, would it not be cool if uniden made a docking station for the 436. put it in and it not only powers the radio BUT ALSO has a larger screen and speaker. turn this into the best portable and base scanner of all time. hhhhhhhmmmm, should work on this idea and send the work to China so i can afford to make it for a profit. lol