| 摘要 |
<p>A document positioning device is provided having a document holder or carrier which is driven by a stepper motor to position a document clamped therein for printing thereon. A row of light sources, e.g. light emitting diodes (LEDs) are pre-positioned and spaced along the path of travel of the document holder so that each source corresponds to a line to be printed on the document. A photosensor is mounted on the document holder for scanning the LEDs. The LED is lit for the selected line to be printed and the stepper motor moves the document holder, scanning the LEDs until coincidence occurs, stopping the motor. A memory is coupled to the motor control circuit of the stepper motor which is activated on coincidence to force the motor control circuit into the proper output for a selected line. For manual operation the LEDs are continually cycled, and the document holder manually moved to the selected line with the power to the motor off. On the selected line standby power is provided, producing an electrical detent action on each line, with the memory insuring the proper position. The positioning device may be actuated by line information contained on a magnetic stripe on the document which is read by a magnetic read/write head assembly. To facilitate the interchanging of documents in different printing apparatus, the write gap is considerably larger than the read gap in the magnetic read/write head.</p> |
