Xbee working over USB but not over external power.

hey guys

i got 2 xbees communicating with each other perfectly over USB but not over external power.

What could be the problem?

Thanx in advance......any help would be appreciated.

but not over external power.

What could be the problem?

Almost certainly the external power. Not enough voltage or current, or mis-wired. What is supplying the external power? What voltage? How much current can the source supply? How is it connected? Do other things the Arduino is doing work? How are the XBees connected to the Arduino?

got it!!
thnx!!!

Could you explain what happened ?? Thx