Complex sentence: The specified speed was 78.26 rpm in America and 77.92 rpm throughout the rest of the world, the difference in speeds was a result of the difference in cycle frequencies of the AC power driving the stroboscopes used to calibrate recording lathes and turntables.
Split into simpler sentences: The specified speed was 78.26 rpm in America and 77.92 rpm throughout the rest of the world. The difference in speeds was a due to the difference in the cycle frequencies of the AC electricity that powered the stroboscopes used to calibrate recording lathes and turntables.