Magnetic tape with optically-read marks on back - corresponding at extremities to smallest and largest number input through keyboard

摘要

Optically-read markings on the backs of magnetic tapes are used to permit the tape recorder user to find a particular position on the tape by in-putting a number through a keyboard. The markings in the form of long and short bars are read by converters which emit impulses, these being compated with the keyboard input in an evaluator. The latter is designed to stop tape movement when scanning of the tape markings show that it is running in the wrong direction. The tape has at the beginning and end of the scanning tracks binary markings equivalent to the smallest e.g. 000 and largest e.g. 999 numbers which can be input through the keyboard. The tape may have both extreme 000/001 and 998/999 values and there may be markings detectable by the evaluator so as to reverse tape movement.