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Data retrieval and error detection circuitry for a width-modulated bar-code scanning apparatus

  • US 3,906,203 A
  • Filed: 09/20/1973
  • Issued: 09/16/1975
  • Est. Priority Date: 09/20/1973
  • Status: Expired due to Term
First Claim
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1. An apparatus for reading width-modulated bar codes comprising:

  • means for generating a time-varying signal whose fluctuations correspond to the spatial fluctuations in said bar code;

    timing means for generating a signal representation of a number proportional to the amount of time which elapses between successive fluctuations in said signal;

    a shift register having an input connected to said signal representation and having a plurality of outputs from successive internal stages;

    means for loading a signal representation into said shift register each time there is a fluctuation in said signal;

    arithmetic means having inputs connecting to said outputs and having an arithmetic output for generating at said arithmetic output a signal representing the sum of or difference between the signals presented to said inputs;

    comparison means having two inputs connecting to two of said outputs and having an output for generating at said output a binary signal whose state indicates which of two inputs is the larger or smaller; and

    a second shift register connected between one of said outputs and said comparison means.

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