was a large rubber roller ("power roll") that rotated continuously at a few hundred rpm. It provided power for typing as well as power-operated backspace, type basket shift, and power for engaging (and probably disengaging) the carriage return clutch. Referring to the photo of the cam assembly (often simply called a cam; it was not meant to be disassembled), the holes in the side plates at the lower left were for the assembly's pivot rod, which was fixed to the frame. At the extreme upper left was part of a disconnectable pivot that pulled down on the typing linkage. As installed, "down" was to the right in the photo. Referring again to the part at the upper left, the mating part had a threaded mounting for adjusting cam clearance from the power roll. The irregular "roundish" part, lower right center, was the cam itself. It rotated in the frame while in contact with the power roll. The surface of the cam in contact with the power roll had grooves for better grip. As the radius at the contact patch increased, the frame rotated clockwise to pull down on the linkage to type the character. This particular cam assembly had a cam that rotated a full turn for each operation; it might operate the backspace, basket shift, or carriage-return clutch disengage mechanism. Cams for typing characters rotated only half a turn, the halves being identical. Below the cam in this photo (hidden) was a spring-loaded lever that pushed against a pin on the cam. On the upper edge of the cam, as shown, was a little projection that engaged the release lever, which was at the lowest part of the image; this was an irregular shape. When a key was pressed down, it moved the release lever and unlatched the cam for that letter; the spring-loaded lever pressing on the pin rotated the cam until it engaged the power roll. As the cam continued to turn, increasing radius rotated the cam's frame slightly (clockwise in the photo) to operate the typing linkage for that character. As the cam continued to rotate, the spring-loaded lever pushed on the pin to move it toward home position, but if the key were still down, the cam (now out of contact with the power roll) stalled because the projection on the cam would catch on another part of the release lever. The cam stalled until