echo

This guy became blind at a very young age, and has learned to use echolocation to get around. I was pretty amazed by all the stuff he is able to do, but at one point in the video they showed him playing video games, and he said he could hear what was going on enough to play. Ok, how the hell can...

I was going to bid on a service manual (CD's) for my car on Ebay however I noticed a neutral comment in the sellers feedback. I contacted this chap who told me the cd's were useless unless you have an 'echo service'...What is it?