Does anyone know how the K&B Torpedo dual needle was supposed to work?

I got one of those (a Green head .15) back in the late '50's by selling greeting cards. Part of a package with a Berkeley Dauntless. I never set it up with both needles, but the idea was that with flow through one needle the engine would run normally fast. Then there was a "switch" that would with run fuel through both needles or through the second one that was set very rich. Hence the engine would slow down. I never had the "switch" but read about the system in a magazine or the included instructions. Way too long ago to remember any details. Surely it did not work well.
Chuck

Ah yes, greeting cards, there were always nice ladies willing to help out a young entrepreneur. Thanks

early way to obtain idle. second needle was mix for idle and you swittched between the two needle for high speed or idle. before the carbs with the rotating barrel that we have now came around.