Abstract: The present invention comprises an apparatus and method for sensing whether a pen is in the grasp of a pen claw of a drawing arm or a plotter or other graphics mechanism. More specifically, the present invention comprises a pen claw movable between an upward position and an downward writing position, the pen claw being connected to a detector which detects both upward and the downward movements of the pen claw. The pen is provided with an annular ring extending therefrom and the plotter mechanism has a stop provided thereon.

Abstract: The present invention comprises a mechanism for incrementally rotating a plotter carousel holding a plurality of pens around its perimeter. The rotational increments of the carousel are spaced to present any of the plurality of pens to a drawing arm on the plotter, or other graphics. A non-servo, non-stepper electric motor, such as a DC motor commonly used in slot cars, provides the rotational power to rotate the carousel. A control device switches the motor on or off with an output connected to the base of a driver connected between the power supply and the motor. The motor, when on, rotates an incremental indexing mechanism that in turn rotates the carousel in increments, each increment being a fraction of one full rotation. A switch is provided which detects that the carousel has been rotated one increment.