This is the Gretsch name for its humbucking pickup, which appeared in 1958, about a year after Gibson started putting humbuckers on their high-end guitars. It replaced the single-coil DeArmond pickups on almost all of the Gretsch line. The FilterTrons had two rows of adjustable pole pieces versus Gibson’s single row and thus could be coaxed into delivering a slightly brighter sound. But the real innovation is one which most guitarists never saw: FilterTrons were connected to the wiring harness inside the guitars by a 3-prong plug. That’s right, no soldering necessary!