The arc welder simulator is made up from several functional blocks: five oscillators, two gates and the output driver.
IC1A, IC1B and IC1C are all wired as square wave oscillators, each operating at a different frequency under 100 Hz. This output is a pulse of semi-random duration and occurring at semi-random intervals. This is used to generate the occasional bright flashes associated with arc welding.
IC1E is also wired as an oscillator operating at a similar frequency to the previous three, though unlike them, its pulse length is adjustable from nearly 0 percent to 50 percent. This is used to generate the consistent flicker. The adjustment is provided