many respects, the simplified model's mechanism was also the simplest to operate.
A crank handle, located on the right side, turned the smaller of the two wheels
(see illus below). The wheel, or disk, had detents at the top and bottom,
and raised or lowered the slides with a small lever and bell crank. When
the slide was in the bottom detent position, the mechanism could be declutched
and the frame changed by merely pushing in
knob. Fancier models required the operating lever be pushed all the way down
and help, or the front door opened to change frames. The mechanism
operates smoothly, with little fuss. In all respects this appears to be
a simple, clever and long lasting arrangement.