As I bring the Fox camera closer to running film for the first time in many years, I thought it was very interesting to show how much thought went into the simple magazine. Anyone who has loaded a film magazine knows the frustrations associated with that process, especially those in the visual effects end of the business. The Cine Simplex magazine has a number of ingenious features, starting with the feed-side clutch that can be turned on and off with a simple screwdriver.
Anyone who has had to backwind film to do an effect knows the struggle with moving belts and readjusting clutches on Mitchell-type magazines. The Simplex magazine eliminates many of these troubles by having the clutch internal to the magazine. A simple slotted on/off switch on the outside of the magazine allows you to easily engage or disengage the clutch. This setup makes it easy to swap the take-up belt between the two chambers of the magazine. The core retaining knob operates a very clever set of pins and keys inside the magazine. Turning the knob retracts the core retaining pins, allowing the core to be installed on the key inside the magazine. When rotated the opposite direction, the pins expand, locking the core in place.
Taking cues from Bell & Howell magazines, the light trap on the Simplex magazine is operated by a pin and cam arrangement that opens and closes the light trap. The latch on the camera door operates a secondary pin on the camera body that pushes the pin on the magazine to open the light traps when the magazine is fully seated on the camera, and the camera door is closed. The Bell & Howell magazine requires a tool to hold the light trap open while you thread the film in the magazine. The Simplex magazine simplifies this by locating the light trap operating pin on the face of the magazine where it is easily accessible with your thumb.
Opening the light trap with my thumb 
Demonstration of the camera door latch light trap pin
The deeper I get into the process of restoring this camera, the more I am impressed with the depth of thought and design that was put into every piece. Having been frustrated shooting numerous different kinds of visual effects that required backwinding, the elegance of this system is wonderful. And having spent time in a darkroom where the core unexpectedly fell out of the magazine, and panic setting in, the solutions the Fox engineers came up with here are ingenious.
