Abstract: A pair of ribbon spools are independently operated by respective motors to rotate in one direction until the ribbon end and then in the opposite direction, and so forth. Spools alternately function as feed and take-up spools and motors as a drive and drag motors, respectively To eliminate excess drag motor cogging, a ribbon tension control system uses dynamic braking of the drag motor, and includes drag circuitry with rectifier bridge circuitry and a constant current sink settable for drawing predefined selectable levels of current from the windings of the drag motor. The motors are polyphase, permanent magnet, stepper motors which, when turned by the ribbon, generate alternating back emf signals in their windings. A full-wave rectifier bridge is connected to each winding of the drag motor with bridge outputs connected to a common sink which is an emitter follower circuit whose current level is set and maintained by an operational amplifier.

Abstract: Tractor drives of a high speed printer move a length of continuous-form paper longitudinally up from a box of fanfold stacked paper, through a print mechanism, across paper directing means, and downward to refold onto a fanfold stack. A misfold detector is positioned at the paper directing means to sense the jumble of paper caused by misfolding prior to jamming of paper movement through the tractor drive to prevent damage to the paper, complex restarting procedures, or data loss.

Abstract: Tractor drives of a high speed printer move a length of continuous-form paper longitudinally up from a box of fanfold stacked paper, through a print mechanism, across paper directing means, and downward to refold onto a fanfold stack. A misfold detector is positioned at the paper directing means to sense the jumble of paper caused by misfolding prior to jamming of paper movement through the tractor drive to prevent damage to the paper, complex restarting procedures, or data loss.