Green driving disk of width w has a tooth groove and a red pin nearby.
Yellow driven gear of width 2w has an even number of standard spur gear teeth. They alternately have full and half-width (mutilated) teeth.
During the dwell period, two full-width teeth are in contact with the circumference of the driving disk, thus locking the gear. The mutilated tooth between them is in front of the driver. At the end of the dwell period, the red pin contacts the mutilated tooth and turns the driven gear around one circular pitch. Then the full-width tooth engages the tooth groove and the driven gear moves around one more pitch. The dwell period starts again and the cycle is repeated. Totally in one revolution of the driver, the driven gear turns two circular pitches.