Well, someone is pulling your leg Liftloop.
The US Patent office (assumes) that you are an engineer when you read the patents, and if you are not, you won't be able to read through the engineer's jargon and the "lines". Here are the US Patents for metal detectors. And not in 10 light years did Whites invent ground balance, Whites wasn't even in existence when it was invented more than 100 years ago. Herr Geiger and Herr Muller of Germany invented the first geiger-counter (AKA Geiger-Muller counters, AKA "particle detectors", and they measured ionizing radiation). Whites had nothing to do with it.
www.eudem.vub.ac.be/publications/files/MDPatentSearch/v1.1/patent_search/Documents/geotech.html
*Heinrich Wilhelm Dove of Germany invented the (first) induction-balance system (AKA "ground-balance) in about the year 1860, but it wasn't used in application to a metal detector until 100 years later, first by done A.H. Pro and Mr Gardiner of Gardiner Electronics. Whites had nothing to do with that either.
The first metal detector was invented by Alexander Graham Bell, the guy who invented the telephone, and in 1881 he tried to locate the bullet shot into President James Garfield. It would have worked, but the detector got confused because Garfield was lying on a metal table. In 1920 Gerhardt Fischer invented the "radio direction-finder" used for accurate navigation, but Fischer didn't apply for a metal detector patent until 1924. His first patent application for a hand-held (hidden) metal detector was in Feb of 1924 but not approved until July 1928.
In 1950 Whites Electronics began trying to build a machine called the "Oremaster Geiger Counter". Charles Garrett invented the first BFO metal detector before that time. Compass Metal Detectors invented the DD searchcoil, and the multi-filter system, plus greater than 8" air depth detectors, done by the MASTER Keith Wills who now owns East Texas Metal Detectors. He is the best metal detector repairman on the planet.
Westinghouse Corporation invented the first application of harmonics (riding on a square wave, or "multiple frequencies") more than a hundred years ago. Minelabs tries to take credit for that, but they didn't invent it. It was invented so that more than one conversation could be achieved on telegraph wires. Don't believe the stories that metal detector manufacturers tell you, they are just trying to make a buck, and you are just a number just like the rest of us are, and they don't care if they stretch the truth a little to sell more metal detectors.
What most people don't know (or accept) is that metal detector manufacturers commonly borrow and steal ideas and plans from each other. It is protocol, and been going on for decades, and that's why there is little difference between one brand and another, save for toys , bells, and whistles.
HH
Larry