Actually, Son of Knock-Finder came first, in late '95. I made one, then got a call from a NasCar type engine builder in North Carolina. When I told him about it, he asked if I could add eight knobs so he could manually adjust timing in each cylinder. He said he would buy one if I could get it ready before Daytona. I added more features and put it into a bigger case, but missed the date a couple weeks. Never heard from him again.
I showed them both to KennyD. He helped get us in a couple issues of Hot Rod in '96, so I offered him a Knock-Finder, he said he would rather have the little one. We called it Son of Knock-Finder because it was smaller.
Both were designed for distributor ignition. I used a timing light pickup to synchronize the unit to the engine.
I intended to price Son of Knock-Finder at $1500. The Knock-Finder was $2495, sold six of them before I stopped making them in 2001. I FedEx'ed a thick package of documents to Circle Track magazine after KennyD tested it, but they didn't return my calls. Guess I'll eat some worms.
I designed the Vampire version in '07, but didn't realize I could show the retarded cylinder until a year later, so the knock-finder option is an add-on daughter board.
The Interceptor version came later, so it has a built in knock-finder. It shows which coils are being retarded, so if you run waste spark it would only show which pair of cylinders are being retarded.
Link to old web page:
http://www.jandssafeguard.com/knockfinder.html