mobyone

I have recently got back into RC and wow things have certainly changed, brushless, lipo, censored, etc... I recently purchased a high voltage (7.4v) servo and put it in my b44.1, I thought since the lipo was 7.4v it would be fine, now I am having problems. After reading thru threads, I guess it is called brown out and I need an external BEC which I have no idea about. I have a Castle Sidewinder ESC and an older KO PROPO receiver. Can some one please shed some light on BEC's? What are they, how they work, how you hook it up and possible suggestions on an affordable model, or a link that will explain things?

Thanks