PG Series of planetary gears are designed for use with the company's new line of brushless dc motors. The first model is available in 42 mm diameter with as many as three gear stages and a wide variety of reduction ratios ranging from 3.65:1 to 393:1. The gear boxes operate with a motor-driven wheel that transmits movement to three circumferential planet gears running in an internally toothed outer ring which forms one stage. They are arranged on the bearing pins of a planet carrier. The last planet carrier in each sequence is rigidly linked to the output shaft ensuring power transmission to the output shaft. Planetary gear design offers higher speed, load and efficiency combined with low backlash in a compact package when compared with spur gears.