Actuator drive and display mechanism

A mechanism for reproducibly coupling a first shaft to a second shaft for coupled rotation in one rotational direction, the mechanism comprising:

• a cam plate which rotates upon rotation of the second shaft, wherein the cam plate includes a face, and a shoulder protruding from the face;
• a cam which rotates upon rotation of the first shaft, wherein the cam includes a face, and a shoulder protruding from the face, where the shoulder of the cam is a mirror image of the shoulder of the cam plate;
• a first spring urges the face of the cam plate in a first axial direction toward the face of the cam, wherein the face of the cam engages the face of the cam plate, and wherein the face of the cam is slidable in a first rotational direction over the face of the cam plate until the shoulders of the cam and cam plate slide over each other and interlock;
• and
• a second spring operably connected to the cam to bias the cam in a second opposite rotational direction to secure the shoulders in an interlocked relation.