 The company's file standard, the Gerber format for PCB files, eventually became an industry standard for describing the printed circuit board images such as the copper layers, solder mask and legend.Early machines used a xenon flash lamp, and projected an image mounted in a rotating "aperture wheel" onto the photosensitive surface of the film or glass plate.The imaging head assembly traversed over the surface of the media without touching it to produce "draws" and "flashes".