The Geneva drive is also called a "Maltese cross mechanism" due to the visual resemblance when the rotating wheel has four spokes.
This intermittent motion is implemented by a Geneva drive, which in turn actuates a claw that engages sprocket holes in the film.
The Geneva drive also provides a precisely repeatable stopped position, which is critical to minimizing jitter in the successive images.
A Geneva drive was used to change filters in the Dawn mission framing camera used to image the asteroid 4 Vesta in 2011.
The external form is the more common, as it can be built smaller and can withstand higher mechanical stresses.
[3]: 128 The figure shows the motion curves for an external four-slot Geneva drive, in arbitrary units.
A discontinuity appears in the acceleration when the drive pin enters and leaves the slot, occurring at the instant the rigid bearing surfaces make contact or separate.