My understanding of it is that it was very simple - an on/off switch and a light on the instrument panel. It worked to about 1,000 yards in a cone from the left boom. I think it did well to detect a persuer and probably very good at detecting someone in formation with you.
I'll have to find this little snippet from an article I have on a Mustang pilot, in it he complains about the system when in formation. But it was a life saver.
I can understand the formation thing. That would piss me off also, everytime some one in my formation came into the arch it would warn me! That would suck.
The P-51D was a great escort fighter and nothing more. The P-47 especially the P-47N and M were better all around fighters than the P-51D and more versatile.